Which method is best for the induction of labour? A systematic review, network meta-analysis and cost-effectiveness analysis

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Chapter 1 Introduction

Chapter 2 Methods for assessment of clinical effectiveness

Chapter 3 Results for assessment of clinical effectiveness

Results of the systematic review

The results of the search and the eligibility assessment are summarised in the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow diagram, which indicates the number of included and excluded trials (Figure 1). We identified 1508 reports corresponding to 1190 separate studies. A total of 611 trials that fulfilled our prespecified inclusion criteria were included in the review. Details of the 579 excluded studies (references and reasons for exclusion) are set out in Appendices 3 and 4, Table 37.

FIGURE 1.

A PRISMA study flow diagram for the systematic review.

There were a total of 103,041 women studied in the 611 trials included in this review. Several multiarm trials were identified: one five-arm trial, four four-arm trials and 42 three-arm trials (see Appendix 6, Table 38). The total number of arms in trials relating to different interventions for the induction of labour is set out in Appendix 10.

It is important to bear in mind that trials may not have reported findings for all of the seven prespecified outcomes. We have indicated, in Table 1, the number of studies reporting each of our prespecified outcomes. Trials that did not report any prespecified outcomes were not included in the review, as they did not contribute data to the pairwise analysis or the NMA (see Appendix 4, Table 37, for reasons for exclusion from the review).

TABLE 1 - Outcome data reported

ICU, intensive care unit; NA, not applicable.

Of our trials, 2 out of 611 were split and data were entered separately for all outcomes because they reported data separately for two different clinical subgroups. This is why we have 613 as the total number of trials here.

Serious maternal morbidity has been defined as uterine rupture or infection requiring ICU admission.

Maternal satisfaction was measured in such a number of different ways that meaningful analysis was not possible.

Outcome	Number of trials reporting this outcome	% included trials (613)a	Number of women/infants	Number of events	Events as %
Serious maternal morbidity or deathb	77	12	19,112	5 deaths 14 uterine rupture 1 ICU admission	0.1
Neonatal death	131	21	32,248	94	0.3
VD not achieved within 24 hours	142	23	28,845	11,885	41.2
Uterine hyperstimulation with (FHR) changes	251	41	43,612	1594	3.6
CS	587	96	99,821	19,297	19.3
Instrumental delivery	302	49	54,511	8020	14.7
NICU admission	226	37	52,931	4224	8.0
Apgar score < 7 at 5 minutes	289	47	58,367	1244	2.1
Maternal satisfactionc	29	5	11,901	NA	NA

More than 95% of trials reported CS, and data were available for almost 100,000 women for this outcome. However, the proportions of trials reporting our other key outcomes were considerably lower: instrumental delivery was reported in approximately half of trials (49%) and infant Apgar score < 7 at 5 minutes was reported in a similar number of studies (47%). Mean Apgar score at 5 minutes was occasionally reported, but there were insufficient studies reporting this outcome for us to be able to use these data.

Uterine hyperstimulation with FHR changes was reported in 41% of trials. A larger number of trials reported outcomes relating to abnormal uterine activity (tachysystole or hypertonus), but we have included data only for those that were clearly associated with changes in FHR and, therefore, matched our outcome definition for inclusion.

Less than one-quarter of trials reported the number of women achieving VD within 24 hours. Neonatal death was reported in 21% of trials (with data for 32,248 babies) and a composite outcome of maternal death or serious morbidity in 12.6%. As expected, event rates were very low for both of these outcomes and most trials reported no events for either outcome.

Infant admission to NICU was reported for trials that, together, included > 50,000 babies, but findings related to this outcome need to be interpreted with some caution. Results demonstrate that there was considerable variation between trials in terms of rates of admission, and it is possible that this variation may relate to definitions of neonatal intensive care and other types of special care units, rather than being a true reflection of variation in serious infant morbidity in different trial settings. There was very rarely clear information on the level of care provided in facilities described as NICU or special care baby unit or on criteria for admission.

Only 29 trials reported any outcomes relating to satisfaction, and the way satisfaction outcomes were defined and operationalised in questionnaires meant that we were unable to carry out any quantitative analysis. We have, therefore, set out findings in tabular and narrative form.

Although Box 2 sets out the number of trials reporting specific outcomes, we were not able to use all of the reported outcome data in the NMA. Studies that reported no events in either arm were excluded from the NMA. In a small number of cases outcome data were excluded from the analysis for other reasons (see Box 2).

BOX 2 - Studies included and excluded from the NMA analysis for each outcome

No vaginal delivery within 24 hours (141 studies included)

Removed because no data reported (471).

Removed because of 100% cells in both arms (1).

Hyperstimulation (180 studies included)

Removed because no data were reported (362).

Removed because of zeros in both arms (71).

Caesarean section (307 studies included)

Removed because no data were reported (26).

Removed because of zero cells in both arms (2).

Removed because of high risk of bias (276).

Removed because of automatic CS after 24 hours (2).

Neonatal death (42 studies included)

Removed because no data were reported (482).

Removed because of zero events in both arms (89).

Maternal serious morbidity or death (16 studies included)

Removed because no data were reported (536).

Removed because of zero cells in both arms (61).

Instrumental delivery (299 studies included)

Removed because no data were reported (311).

Removed because of zero cells in both arms (2).

Removed because of serious protocol deviation (1).

Apgar score < 7 at 5 minutes (200 studies included)

Removed because no data were reported (324).

Removed because of zero cells in both arms (81).

Removed because of inconsistency in reporting (8).

Neonatal intensive care unit admission (204 studies included)

Removed because no data were reported (387).

Removed because of zero cells in both arms (21).

Characteristics of women participating in included trials

Summary characteristics of participants and intervention setting across the 611 included studies are reported in Table 2.

TABLE 2 - Number of included clinical trials reporting participant characteristics

NR, not reported.

Effect modifier	Number of trials
Parity	Mixed	Multiparous only	Nulliparous only	NR
	456	15	79	63
Previous CS	None with CS	All with CS	Some with CS	NR
	396	5	37	175
Cervix	Unfavourable	Favourable	Mixed	NR
	399	28	111	75
Membranes	All intact	All ruptured	Mixed	NR
	296	98	68	151
Gestational age	All post term	All > 37 weeks	Mixed (some pre term)	NR
	72	333	149	59
Multiple pregnancy	All singleton	All multiple	Mixed	NR
	453	1	13	146
Setting	Inpatient	Some/all arms outpatient	NR
	524	79	10
Pharmaceutical company funding	No funding	Some funding	NR
	109	55	449

Trials varied considerably in terms of inclusion/exclusion criteria. For those trials that reported parity as an inclusion criterion, most (83%) recruited both women expecting their first baby and those who had given birth before. More than two-thirds of trials explicitly excluded women who had experienced a previous CS (64.6%). However, 175 trials did not specifically mention excluding these women but may have reported excluding women at ‘high risk’, which may have included women with complications during a previous birth. Women with multiple pregnancies were generally excluded. The majority of trials (73%) that specified inclusion criteria relating to gestational age specifically excluded women at < 37 completed weeks’ gestation. Of these 405 trials, 72 recruited women with post-term pregnancies only, usually defined as gestational age of > 41 weeks. Other trials included a small number of women with preterm pregnancies, although we specifically excluded trials including women with extremely preterm pregnancies as our focus was on third-trimester induction of labour.

Most studies recruited women with intact membranes (64% of those trials specifying inclusion criteria relating to membrane status), although some trials specifically focused on induction of labour for women with premature rupture of the amniotic membranes (21% of trials specifying membrane status).

Finally, the induction process was mainly commenced in those women with a Bishop score < 6 (unfavourable cervix); 28 trials (4.6%) recruited only women with a favourable cervix, although approximately 20% of trials that described membrane status at recruitment included women with a range of Bishop scores.

Other trial characteristics

The vast majority of trials were carried out in hospital settings and women remained inpatients throughout the induction process. For many pharmacological agents constant maternal and fetal monitoring was considered mandatory, and facilities for CS and newborn specialist care were close by in case of complications. Trials looking at non-pharmacological methods of inducing labour (e.g. membrane sweeping) were more likely to take place in outpatient settings.

Trials were assessed for risk of bias relating to the method used to conceal allocation. There was a fairly even balance between those trials assessed as being at low risk of bias and those assessed as being at high or unclear risk of bias (both of these categories were treated as high risk of bias in the sensitivity analysis). There were 300 trials that were judged to be at high risk of bias for allocation concealment compared with 313 trials that were judged to be at low risk of bias.

Finally, we also extracted information from trial reports regarding whether or not the trial was funded by a pharmaceutical company. Unfortunately, the source of funding for most trials was not reported. Of the 164 trials that did report source of funding, one-third were funded by a drug company, although this funding may have been partial (provision of study medication and placebo preparations only).

Results: network and pairwise meta-analysis

The outcome-specific network diagrams are presented in Figure 2 for failure to achieve VD in 24 hours, Figure 3 for CS, Figure 4 for instrumental delivery, Figure 5 for uterine hyperstimulation, Figure 6 for NICU admission and Figure 7 for Apgar score < 7 at 5 minutes. Studies were excluded when there were 0% or 100% events in every arm, for that outcome only. Network diagrams are presented within each relevant section and by outcome. The edges (lines) connecting each pair of interventions represent a direct comparison and are drawn proportional to the number of trials making each direct comparison. 953 However, this weighting is relative within each graph, and edge thickness should not be compared across graphs. For information on the number of trials in each analysis please see Appendix 14. As noted above (see Results of the systematic review), there were insufficient data on serious maternal morbidity or death (20 events) to be used in a NMA. Therefore, these data are summarised narratively below (see Neonatal and maternal mortality and severe morbidity). In addition, only a small proportion of trials reported outcomes relating to women’s perceptions of their care during childbirth and their satisfaction with the induction of labour process. Furthermore, when these outcomes were reported they were defined and measured in different ways across trials. For these reasons we were not able to analyse maternal satisfaction outcomes in a NMA, but we have included a narrative description in the text (see Maternal satisfaction with care and induction of labour method).

FIGURE 2.

Failure to achieve VD in 24 hours. Network diagram of all of the studies included in analysis. The width of the lines is proportional to the number of trials comparing directly each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). Interventions are numbered as follows: 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, intracervical PGE₂; 7, vaginal PGE₂ pessary (normal release); 8, vaginal misoprostol (dose < 50 µg); 9, vaginal misoprostol (dose ≥ 50 µg); 10, oral misoprostol tablet (dose < 50 µg); 11, oral misoprostol tablet (dose ≥ 50 µg); 12, titrated (low-dose) oral misoprostol solution; 13, sustained-release misoprostol insert; 14, i.v. oxytocin; 15, i.v. oxytocin with amniotomy; 16, NO; 17, mifepristone; 18, mechanical methods – Foley catheter; 19, mechanical methods – double-balloon or Cook’s catheter; 20, extra-amniotic PGE₂; 21, buccal/sublingual misoprostol.

FIGURE 3.

Caesarean section. Network diagram of all of the studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). Interventions are numbered as follows: 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, PGF₂ gel; 7, intracervical PGE₂; 8, vaginal PGE₂ pessary (normal release); 9, vaginal misoprostol (< 50 µg); 10, vaginal misoprostol (≥ 50 µg); 11, oral misoprostol tablet (< 50 µg); 12, oral misoprostol tablet (≥ 50 µg); 13, titrated (low-dose) oral misoprostol solution; 14, sustained-release misoprostol insert, 15, i.v. oxytocin, 16, amniotomy; 17, i.v. oxytocin with amniotomy; 18, NO; 19, mifepristone; 20, oestrogens; 21, corticosteroids; 22, relaxin; 23, hyaluronidase; 24, Foley catheter; 25, laminaria; 26, double-balloon or Cook’s catheter; 27, membrane sweeping; 28, extra-amniotic PGE₂; 29, i.v. prostaglandin; 30, sexual intercourse; 31, acupuncture; 32, oral prostaglandins; 33, buccal/sublingual misoprostol.

FIGURE 4.

Instrumental delivery. Network diagram of all of the studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). Interventions are numbered as follows: 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, PGF₂ gel; 7, intracervical PGE₂; 8, vaginal PGE₂ pessary (normal release); 9, vaginal misoprostol (< 50 µg); 10, vaginal misoprostol (≥ 50 µg); 11, oral misoprostol tablet (< 50 µg); 12, oral misoprostol tablet (≥ 50 µg); 13, titrated (low-dose) oral misoprostol solution; 14, sustained-release misoprostol insert; 15, i.v. oxytocin; 16, amniotomy; 17, i.v. oxytocin with amniotomy; 18, NO; 19, mifepristone; 20, oestrogens; 21, relaxin; 22, Foley catheter; 23, laminaria; 24, double-balloon or Cook’s catheter; 25, membrane sweeping; 26, extra-amniotic PGE₂; 27, i.v. prostaglandin; 28, sexual intercourse; 29, acupuncture; 30, homeopathy; 31, oral prostaglandins; 32, buccal/sublingual misoprostol.

FIGURE 5.

Hyperstimulation with FHR changes. Network diagram of all of the studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, intracervical PGE₂; 7, vaginal PGE₂ pessary (normal release); 8, vaginal misoprostol (< 50 µg); 9, vaginal misoprostol (≥ 50 µg); 10, oral misoprostol tablet (< 50 µg); 11, oral misoprostol tablet (≥ 50 µg); 12, titrated (low-dose) oral misoprostol solution; 13, sustained-release misoprostol insert; 14, i.v. oxytocin; 15, i.v. oxytocin with amniotomy; 16, NO; 17, mifepristone; 18, Foley catheter; 19, laminaria; 20, double-balloon or Cook’s catheter; 21, buccal/sublingual misoprostol.

FIGURE 6.

Neonatal intensive care unit admission. Network diagram of all of the studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, PGF₂ gel; 7, intracervical PGE₂; 8, vaginal PGE₂ pessary (normal release); 9, vaginal misoprostol (dose < 50 µg); 10, vaginal misoprostol (dose ≥ 50 µg); 11, oral misoprostol tablet (dose < 50 µg); 12, oral misoprostol tablet (dose ≥ 50 µg); 13, titrated (low-dose) oral misoprostol solution; 14, sustained-release misoprostol insert; 15, i.v. oxytocin; 16, amniotomy; 17, i.v. oxytocin with amniotomy; 18, NO; 19, mifepristone; 20, oestrogens; 21, Foley catheter; 22, laminaria; 23, double-balloon or Cook’s catheter; 24, membrane sweeping; 25, extra-amniotic PGE₂; 26, sexual intercourse; 27, acupuncture; 28, oral prostaglandins; 29, buccal/sublingual misoprostol.

FIGURE 7.

Apgar score < 7 at 5 minutes. Network diagram of all of the studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). 1, no treatment; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, intracervical PGE₂; 7, vaginal PGE₂ pessary (normal release); 8, vaginal misoprostol (dose < 50 µg); 9, vaginal misoprostol (dose ≥ 50 µg); 10, oral misoprostol tablet (dose < 50 µg); 11, oral misoprostol tablet (dose ≥ 50 µg); 12, titrated (low-dose) oral misoprostol solution; 13, sustained-release misoprostol insert; 14, i.v. oxytocin; 15, amniotomy; 16, i.v. oxytocin with amniotomy; 17, NO; 18, mifepristone; 19, Foley catheter; 20, laminaria; 21, double-balloon or Cook’s catheter; 22, membrane sweeping; 23, extra-amniotic PGE₂; 24, i.v. prostaglandin; 25, sexual intercourse; 26, acupuncture; 27, oral prostaglandins; 28, buccal/sublingual misoprostol.

Vaginal delivery not achieved within 24 hours

After excluding trials with zero events in all arms, 141 trials of 19 active interventions were included for the outcome VD not achieved within 24 hours. Placebo and no intervention comparisons were also included. No trials comparing PGF₂, amniotomy, oestrogens, corticosteroids, relaxin, hyaluronidase, laminaria, membrane sweeping, i.v. prostaglandin, sexual intercourse, acupuncture, breast stimulation, homeopathy, castor oil or oral prostaglandins reported this outcome. No meaningful differences were observed in posterior mean residual deviance or DIC values, suggesting that there was no evidence of inconsistency (see Appendix 11, Table 44). Reported results are therefore based on the REs NMA model assuming consistency (Table 3 and Figure 8).

TABLE 3 - Odds ratios and 95% CrI for failure to achieve VD within 24 hours for every intervention compared with placebo

Results from NMA and pairwise meta-analysis (when possible). An OR of > 1 favours placebo (i.e. fewer events occur on a placebo than active intervention). An OR of < 1 favours the active intervention, i.e. fewer undesirable events occurred on the active intervention. Empty cells indicate that direct evidence was not available for that comparison. The column ‘Direct trials’ reports the number of trials available for the direct comparisons vs. placebo only.

Active intervention vs. placebo	NMA		Pairwise meta-analysis		Direct trials
	OR	95% CrI	OR	95% CrI
i.v. oxytocin with amniotomy	0.05	0.07 to 0.32	–	–	0
Vaginal misoprostol ≥ 50 µg	0.09	0.06 to 0.24	–	–	0
Titrated (low-dose) oral misoprostol solution	0.10	0.07 to 0.29	–	–	0
Vaginal misoprostol < 50 µg	0.11	0.09 to 0.32	–	–	0
Sustained-release misoprostol vaginal pessary	0.11	0.05 to 0.22	–	–	0
Buccal/sublingual misoprostol	0.11	0.05 to 0.19	–	–	0
Vaginal PGE2 pessary (normal release)	0.11	0.04 to 0.16	0.67	0.06 to 2.76	1
Vaginal PGE2 (gel)	0.13	0.08 to 0.50	–	–	0
Vaginal PGE2 pessary (slow release)	0.15	0.08 to 0.29	–	–	0
Oral misoprostol tablet ≥ 50 µg	0.16	0.05 to 0.20	0.12	0.03 to 0.31	2
Vaginal PGE2 (tablet)	0.16	0.03 to 0.26	–	–	0
Intracervical PGE2	0.18	0.09 to 0.38	0.09	0.03 to 0.19	5
Double-balloon or Cook’s catheter	0.18	0.01 to 0.16	–	–	0
Foley catheter	0.19	0.09 to 0.46	–	–	0
i.v. oxytocin	0.20	0.21 to 1.97	–	–	0
NO	0.22	0.08 to 0.36	1.07	0.30 to 2.78	1
Oral misoprostol tablet < 50 µg	0.22	0.07 to 0.39	–	–	0
Extra-amniotic PGE2	0.41	0.07 to 1.33	–	–	0
Mifepristone	0.76	0.05 to 0.20	0.81	0.16 to 2.52	1

FIGURE 8.

Rankograms for each of the 20 induction interventions for hyperstimulation and VD not achieved within 24 hours. Ranking indicates the probability of being the best intervention, the second best, the third best, etc. The x-axis shows the relative ranking and the y-axis the probability of each ranking. (a) No treatment; (b) placebo; (c) vaginal PGE₂ (tablet); (d) vaginal PGE₂ (gel); (e) vaginal PGE₂ pessary (slow release); (f) intracervical PGE₂; (g) vaginal PGE₂ pessary (normal release); (h) vaginal misoprostol (dose < 50 µg); (i) vaginal misoprostol (dose ≥50 µg); (j) oral misoprostol tablet (dose < 50 µg); (k) oral misoprostol tablet (dose ≥ 50 µg); (l) titrated (low-dose) misoprostol; (m) sustained-release misoprostol insert; (n) i.v. oxytocin; (o) NO; (p) i.v. oxytocin with amniotomy; (q) mifepristone; (r) Foley catheter; (s) laminaria including dilapan; (t) double balloon or Cook’s catheter; and (u) extra-amniotic PGE₂.

Despite the observation of high between-trials heterogeneity, relative to the size of the intervention effect estimates, [τ = 0.54 (95% CrI 0.44 to 0.65)] there was strong evidence that all interventions, except for mifepristone and extra-amniotic PGE₂, increased the probability of vaginal birth within 24 hours (see Table 3). We note that there was some indication that the direct and NMA results were inconsistent for NO, as the point estimate from the NMA (OR 0.21) lies outside the CrI from the direct evidence (95% CrI 0.30 to 2.78). However, the CrIs for both the NMA and direct evidence were overlapping. The full results of each intervention compared with every other have been reported in Appendix 12 (see Table 50) and compared with the direct evidence when it is available.

Figure 8 shows the distribution of the ranks for each of the 20 interventions. The x-axis reports each of the possible ranks, for which position 1 means that the intervention is ranked the highest and position 21 the lowest. Note the number of interventions varies across outcomes because of trial design and reporting. The y-axis shows the probability with which each intervention has been ranked at each of the 21 possible positions and therefore fully encapsulates the uncertainty in the intervention rankings. The peaks in the rankogram plots show the most likely rank for a given intervention. Flat lines indicate a high degree of uncertainty for the ranking of that intervention type.

The highest ranked intervention was i.v. oxytocin with amniotomy, with a probability of being best of 75%, a posterior mean rank of ‘2’ (95% CrI 1 to 10) and an OR of 0.05 (95% CrI 0.01 to 0.14). Intravenous oxytocin with amniotomy had the lowest absolute probability of not achieving VD within 24 hours at 17% (95% CrI 3% to 44%) (Table 4). The probability of being ranked in the top three interventions was 88% for i.v. oxytocin with amniotomy, 51% for vaginal misoprostol (≥ 50 µg) (posterior mean rank 4 (95% CrI 2 to 7), and 50% for vaginal PGE₂ pessary (normal release) (posterior mean rank 4 (95% CrI 1 to 11). The probability of being ranked in the bottom three interventions (i.e. poorest in terms of achieving a vaginal birth within 24 hours) was 80% for mifepristone with a posterior mean rank of 19 (95% CrI 17 to 21). We note from Table 3 that for mifepristone the OR is 0.72 and the 95% CrIs are consistent with both harm and benefit (0.20 to 1.85).

TABLE 4 - Absolute probability of VD not occurring within 24 hours of induction for all 19 interventions and placebo/no intervention included in the NMA. Posterior mean rank and 95% CrIs

Intervention	Absolute probability of VD not in 24 hours		Posterior mean rank	95% CrI
	Posterior mean	95% CrI
i.v. oxytocin with amniotomy	0.33	0.11 to 0.61	2	1 to 9
Vaginal misoprostol ≥ 50 µg	0.48	0.34 to 0.61	3	1 to 6
Sustained-release misoprostol vaginal pessary	0.50	0.27 to 0.73	5	1 to 16
Titrated (low) oral misoprostol solution	0.50	0.34 to 0.67	5	1 to 10
Vaginal misoprostol < 50 µg	0.51	0.37 to 0.65	5	2 to 8
Buccal/sublingual misoprostol	0.51	0.35 to 0.67	5	2 to 11
Vaginal PGE2 pessary (normal release)	0.52	0.34 to 0.70	6	1 to 13
Vaginal PGE2 (gel)	0.57	0.42 to 0.70	8	5 to 12
Vaginal PGE2 pessary (slow release)	0.60	0.45 to 0.74	11	6 to 16
Vaginal PGE2 (tablet)	0.62	0.53 to 0.70	11	5 to 17
Oral misoprostol tablet ≥ 50 µg	0.62	0.48 to 0.75	12	7 to 16
Double-balloon or Cook’s catheter	0.63	0.44 to 0.80	12	4 to 18
Foley catheter	0.65	0.48 to 0.79	13	7 to 18
Intracervical PGE2	0.65	0.51 to 0.77	14	10 to 17
i.v. oxytocin	0.66	0.51 to 0.80	14	9 to 18
Oral misoprostol tablet < 50 µg	0.67	0.46 to 0.84	14	5 to 18
NO	0.68	0.46 to 0.84	14	5 to 18
Extra-amniotic PGE2	0.75	0.44 to 0.93	16	3 to 20
Mifepristone	0.86	0.66 to 0.96	19	16 to 21
No intervention	0.91	0.83 to 0.96	20	19 to 21
Placebo	0.94	0.86 to 0.98	21	19 to 21

Results were largely robust to a preplanned sensitivity analysis excluding studies at high risk of bias for allocation concealment. The posterior mean ranks were altered for two interventions. A posterior mean rank for vaginal PGE₂ pessary (normal release) changed from 4 to 10, although the 95% CrIs were still overlapping. Sustained-release misoprostol insert changed from 5 to 10. Again 95% CrIs were consistent between the two analyses. Results for the sensitivity analysis are reported in Appendix 13 (see Table 56).

Caesarean section

After the exclusion of trials with 0% or 100% events in all arms, 586 trials with 96,771 women were eligible for inclusion in the NMA. This included 33 active interventions in addition to placebo and no intervention.

Important differences were observed in posterior mean residual deviance and DIC values suggesting that, for the full network, there was evidence of inconsistency (see Appendix 11, Table 45). The addition of a continuity correction of 0.5 for studies with zero events (on either arm) did not improve model fit. We conducted a prespecified sensitivity analysis examining the effect of removing trials at high risk of bias. The REs model, continuity corrected and excluding trials at high risk of bias, provided an adequate fit to the data (see Appendix 11, Table 45). Therefore, reported results are based on this model, with 307 trials and 57,370 women (see Tables 5 and 6, and Figure 3). Thirty-one interventions, in addition to placebo and no intervention are included in the analysis. No trials comparing breast stimulation, homeopathy or castor oil were included in this analysis because of a high risk of bias.

TABLE 5 - Odds ratios and 95% CrI for CS for every intervention compared with placebo

Results from NMA and pairwise meta-analysis (when possible). An OR of > 1 favours placebo (i.e. fewer CSs occur on a placebo than active intervention). An OR of < 1 favours the active intervention, i.e. fewer CSs occurred on the active intervention. Empty cells indicate that direct evidence was not available for that comparison. The column ‘trials’ reports the number of trials available for the direct comparisons vs. placebo only.

Active intervention vs. placebo	NMA		Pairwise meta-analysis
	OR	95% CrI	OR	95% CrI	Trials
Corticosteroids	0.53	0.20 to 1.12	0.72	0.25 to 1.65	1
Hyaluronidase	0.61	0.34 to 1.00	0.24	0.10 to 0.46	1
Titrated (low-dose) oral misoprostol solution	0.62	0.47 to 0.80	–	–	0
Buccal/sublingual misoprostol	0.68	0.51 to 0.89	–	–	0
PGF2 gel	0.70	0.40 to 1.16	0.65	0.27 to 1.30	3
Vaginal misoprostol < 50 µg	0.70	0.57 to 0.85	1.14	0.58 to 2.05	3
Mifepristone	0.71	0.45 to 1.08	0.63	0.39 to 0.95	5
Oral misoprostol tablet ≥ 50 µg	0.72	0.58 to 0.88	0.60	0.35 to 0.96	6
Oral prostaglandins	0.72	0.08 to 2.59	–	–	0
Vaginal misoprostol ≥ 50 µg	0.73	0.59 to 0.88	1.32	0.17 to 4.64	2
Membrane sweeping	0.74	0.53 to 0.99	1.78	0.22 to 6.41	1
Foley catheter	0.76	0.61 to 0.95	–	–	0
Vaginal PGE2 (gel)	0.79	0.65 to 0.94	0.95	0.63 to 1.37	10
Laminaria	0.80	0.43 to 1.38	–	–	0
Acupuncture	0.81	0.52 to 1.20	0.76	0.46 to 1.16	4
NO	0.82	0.62 to 1.06	1.05	0.70 to 1.49	4
Vaginal PGE2 pessary (normal release)	0.82	0.62 to 1.09	0.76	0.41 to 1.29	3
Intracervical PGE2	0.83	0.69 to 0.98	0.85	0.66 to 1.09	17
Sexual intercourse	0.85	0.54 to 1.29	–	–	0
Relaxin	0.88	0.33 to 1.98	0.90	0.32 to 2.03	3
i.v. oxytocin with amniotomy	0.89	0.57 to 1.34	–	–	0
i.v. oxytocin	0.93	0.75 to 1.14	1.74	0.53 to 4.29	1
Vaginal PGE2 pessary (slow release)	0.89	0.69 to 1.12	0.62	0.26 to 1.21	2
Sustained-release misoprostol vaginal pessary	0.98	0.59 to 1.55	–	–	0
Extra-amniotic PGE2	0.98	0.57 to 1.57	0.47	0.16 to 1.03	3
Vaginal PGE2 (tablet)	1.04	0.78 to 1.35	0.91	0.00 to 5.74	1
Amniotomy	1.06	0.51 to 2.02	–	–	0
Double-balloon or Cook’s catheter	1.11	0.73 to 1.63	–	–	0
Oral misoprostol tablet < 50 µg	1.11	0.64 to 1.81	–	–	0
Oestrogens	1.27	0.62 to 2.32	1.97	0.66 to 4.49	1
i.v. prostaglandin	19.94	1.61 to 120.5	–	–	0

TABLE 6 - Absolute probability of CS all 31 interventions and placebo/no intervention included in the NMA

Intervention	Absolute probability of CS		Posterior mean rank and 95% CrI
	Posterior mean	95% CrI
Corticosteroids	0.15	0.02 to 0.48	6	1 to 29
Titrated (low-dose) oral misoprostol solution	0.17	0.03 to 0.49	6	2 to 13
Hyaluronidase	0.17	0.02 to 0.50	7	1 to 26
Oral prostaglandins	0.17	0.01 to 0.61	10	1 to 32
Buccal/sublingual misoprostol	0.19	0.03 to 0.52	9	2 to 19
Vaginal misoprostol < 50 µg	0.19	0.03 to 0.52	9	4 to 16
Oral misoprostol tablet ≥ 50 µg	0.19	0.03 to 0.53	10	4 to 18
Mifepristone	0.19	0.03 to 0.54	11	2 to 28
Vaginal misoprostol ≥ 50 µg	0.19	0.03 to 0.53	11	5 to 18
PGF2 gel	0.19	0.03 to 0.54	11	1 to 29
Membrane sweeping	0.20	0.03 to 0.54	12	3 to 24
Foley catheter	0.20	0.03 to 0.55	14	6 to 22
Vaginal PGE2 (gel)	0.21	0.03 to 0.55	15	9 to 21
Laminaria	0.21	0.03 to 0.57	15	2 to 31
Acupuncture	0.21	0.03 to 0.57	16	2 to 30
NO	0.21	0.03 to 0.57	17	5 to 28
Sexual intercourse	0.21	0.03 to 0.58	17	3 to 31
Intracervical PGE2	0.21	0.04 to 0.57	18	11 to 24
Vaginal PGE2 pessary (normal release)	0.21	0.03 to 0.57	17	6 to 28
Relaxin	0.22	0.03 to 0.61	16	1 to 32
i.v. oxytocin with amniotomy	0.22	0.04 to 0.59	20	4 to 31
Vaginal PGE2 pessary (slow release)	0.22	0.04 to 0.58	21	12 to 28
No intervention	0.22	0.04 to 0.58	21	13 to 27
i.v. oxytocin	0.23	0.04 to 0.59	23	16 to 29
Placebo	0.24	0.04 to 0.61	26	19 to 31
Sustained-release misoprostol vaginal pessary	0.24	0.04 to 0.61	22	5 to 32
Extra-amniotic PGE2	0.24	0.04 to 0.62	22	4 to 32
Amniotomy	0.25	0.04 to 0.64	22	3 to 32
Vaginal PGE2 (tablet)	0.25	0.05 to 0.62	26	17 to 31
Oral misoprostol tablet < 50 µg	0.26	0.04 to 0.64	25	7 to 32
Double-balloon or Cook’s catheter	0.26	0.05 to 0.64	27	14 to 32
Oestrogens	0.28	0.05 to 0.68	27	5 to 32
i.v. prostaglandin	0.66	0.16 to 0.98	33	32 to 33

Table 5 reports the posterior median ORs (95% CrI) for each intervention relative to placebo (the full results for all comparisons are reported in Appendix 12, Table 51). As an informal check of consistency, we note that for all interventions, the direct and NMA results are similar. Moderate to low between-trial heterogeneity was observed for this outcome [τ = 0.16 (95% CrI 0.03 to 0.25)]. Using placebo as the reference, nine interventions resulted in significant reduction in CS, namely vaginal PGE₂ (gel), intracervical PGE₂, vaginal misoprostol tablet < 50 µg, vaginal misoprostol tablet ≥ 50 µg, oral misoprostol tablet ≥ 50 µg, titrated (low-dose) oral misoprostol solution, Foley catheter, membrane sweeping and buccal/sublingual misoprostol.

Corticosteroids, titrated (low-dose) oral misoprostol solution and hyaluronidase have the largest reduction in odds of CS, but only misoprostol oral solution reached a conventional level of statistical significance. Conversely, i.v. prostaglandin appears to increase odds of CS, although this does not reach statistical significance.

Table 6 reports the posterior mean ranks and absolute probabilities for CS. The interventions with the lowest posterior mean rank (6) were titrated (low-dose) oral misoprostol solution and corticosteroids, with the lowest absolute probability of all interventions at 17% and 15%, respectively. However, the wide CrIs around summary estimates suggest considerable uncertainty. The intervention with the worst posterior mean rank is i.v. prostaglandin ranked 33 (95% CrI 32 to 33) and an absolute probability of CS of 66%, albeit with wide CrIs (95% CrI 16% to 98%).

Figure 9 reports the rankograms for this outcome. We note that for all of the interventions the rankograms are flat, with relatively low peaks – indicative of considerable uncertainty around the probability any intervention is the ‘best’. We do not therefore include an assessment of which probability is best in our summary for CS.

FIGURE 9.

Rankograms for each of the 33 induction interventions for CS and instrumental delivery. Ranking indicates the probability of being the best intervention, the second best, the third best, etc. (a) No treatment; (b) placebo; (c) vaginal PGE₂ (tablet); (d) vaginal PGE₂ (gel); (e) vaginal PGE₂ pessary (slow release); (f) PGF₂ gel; (g) intracervical PGE₂; (h) vaginal PGE₂ pessary (normal release); (i) vaginal misoprostol (dose < 50 µg); (j) vaginal misoprostol (dose ≥ 50 µg); (k) oral misoprostol tablet (dose < 50 µg); (l) oral misoprostol tablet (dose ≥ 50 µg); (m) titrated (low-dose) misoprostol; (n) sustained-release misoprostol insert; (o) i.v. oxytocin; (p) amniotomy; (q) i.v. oxytocin with amniotomy; (r) NO; (s) mifepristone; (t) oestrogens; (u) corticosteroids; (v) relaxin; (w) hyaluronidase; (x) Foley catheter; (y) laminaria including dilapan; (z) double balloon or Cook’s catheter; (aa) membrane sweeping; (ab) extra-amniotic PGE₂; (ac) i.v. prostaglandin; (ad) sexual intercourse; (ae) oral prostaglandins; (af) buccal/sublingual misoprostol; and (ag) acupuncture.

Instrumental delivery

After the exclusion of trials with 0% or 100% events in all arms, 299 trials were included in the NMA for the instrumental delivery outcome (see Figure 4). There were no trials remaining that compared corticosteroids, hyaluronidase, breast stimulation or castor oil. Model fit statistics for the model assuming consistency were indicative of a lack of fit, but this was judged to be borderline. The residual deviance indicated a slight improvement in fit for the model assuming inconsistency. This was accompanied by an increase in heterogeneity and a higher DIC. On balance, therefore, a REs NMA model assuming consistency was still preferred (see Appendix 11, Table 46). Reported results are based on this model, with 299 trials and 32 interventions (see Table 7 and Figure 4).

Table 7 reports the posterior median ORs (95% CrI) for each intervention relative to placebo (the full results are reported in Appendix 12, Table 52). As a further check of consistency, we note that for all of the interventions the direct and NMA results are similar. Using placebo as the reference intervention two interventions resulted in significant reduction in instrumental delivery, namely vaginal PGE₂ pessary (slow release) and Foley catheter.

TABLE 7 - Odds ratios and 95% CrI for instrumental delivery for every intervention compared with placebo

Results from NMA and pairwise meta-analysis (when possible). An OR of > 1 favours placebo (i.e. fewer events occur on a placebo than active intervention). An OR of < 1 favours the active intervention, i.e. fewer events occurred on the active intervention. Empty cells indicate that direct evidence was not available for that comparison. The column ‘Direct trials’ reports the number of trials available for the direct comparisons vs. placebo only.

Active intervention vs. placebo	NMA		Pairwise meta-analysis
	OR	95% CrI	OR	95% CrI	Direct trials
Oestrogens	0.68	0.32 to 1.28	0.75	0.25 to 1.71	1
Mechanical methods – Foley catheter	0.68	0.50 to 0.91	–	–	0
Buccal/sublingual misoprostol	0.69	0.44 to 1.03	–	–	0
Vaginal PGE2 pessary (slow release)	0.72	0.50 to 0.99	1.05	0.40 to 2.26	2
Oral misoprostol tablet < 50 µg	0.74	0.34 to 1.38	–	–	0
Oral prostaglandins	0.74	0.45 to 1.16	–	–	0
Double-balloon or Cook’s catheter	0.75	0.47 to 1.14	–	–	0
Vaginal misoprostol < 50 µg	0.80	0.59 to 1.05	0.64	0.09 to 2.23	1
Mechanical methods – laminaria	0.83	0.47 to 1.38	–	–	0
Acupuncture	0.83	0.51 to 1.26	1.08	0.57 to 1.85	3
Oral misoprostol tablet ≥ 50 µg	0.84	0.63 to 1.09	0.54	0.25 to 1.00	5
PGF2 gel	0.86	0.58 to 1.25	0.74	0.43 to 1.20	3
Amniotomy	0.86	0.50 to 1.38	–	–	0
Intracervical PGE2	0.89	0.68 to 1.14	1.09	0.61 to 1.79	6
Vaginal PGE2 (tablet)	0.91	0.67 to 1.22	–	–	0
Extra-amniotic PGE2	0.91	0.49 to 1.52	0.88	0.32 to 1.91	3
Vaginal misoprostol ≥ 50 µg	0.92	0.70 to 1.18	1.21	0.35 to 3.12	2
NO	0.92	0.69 to 1.21	0.91	0.61 to 1.28	2
Vaginal PGE2 (gel)	0.93	0.72 to 1.18	1.18	0.38 to 2.85	3
Sustained-release misoprostol vaginal pessary	0.93	0.46 to 1.71	–	–	0
i.v. oxytocin with amniotomy	0.93	0.64 to 1.31	–	–	0
Titrated (low-dose) oral misoprostol solution	1.00	0.62 to 1.52	–	–	0
Vaginal PGE2 pessary (normal release)	1.08	0.79 to 1.45	0.98	0.50 to 1.75	3
i.v. oxytocin	1.08	0.83 to 1.39	–	–	0
Membrane sweeping	1.20	0.84 to 1.66	15.45	1.56 to 71.26	1
Sexual intercourse	1.29	0.68 to 2.24	–	–	0
Relaxin	1.44	0.66 to 2.78	1.45	0.65 to 2.87	3
Mifepristone	1.68	1.05 to 2.59	1.84	1.08 to 2.98	5
i.v. prostaglandin	2.04	0.85 to 4.12	–	–	0
Homeopathy	2.13	0.11 to 10.24	2.18	0.09 to 11.64	1

Table 8 reports the posterior mean ranks and absolute probabilities for instrumental delivery. The intervention with the lowest mean rank (6) was Foley catheter, with a 95% CrI ranging from 2 to 12 (of 30 interventions). This intervention had lowest absolute probability of 13% (95% CrI 5% to 28%) jointly with oestrogen (95% CrI 4% to 31%) and buccal/sublingual misoprostol (95% CrI 5% to 29%). However, we note that although the posterior mean rank was ‘8’ for oestrogen and ‘7’ for buccal/sublingual misoprostol, respective 95% CrI were wide (oestrogen: 1 to 28 and buccal misoprostol: 1 to 20). This uncertainty is also reflected in the CrIs around the ORs for these interventions in Table 7. The intervention with the highest absolute probability of instrumental delivery (i.e. worst) was i.v. prostaglandin at 30% (95% CrI 10% to 58%).

TABLE 8 - Absolute probability of instrumental delivery across all 30 interventions and placebo/no intervention included in the NMA. Posterior mean rank and 95% CrIs

Intervention	Absolute probability of instrumental delivery		Posterior mean rank and 95% CrI
	Posterior mean	95% CrI
Oestrogens	0.13	0.04 to 0.31	8	1 to 28
Foley catheter	0.13	0.05 to 0.28	6	2 to 12
Buccal/sublingual misoprostol	0.13	0.05 to 0.29	7	1 to 20
Vaginal PGE2 pessary (slow release)	0.14	0.05 to 0.29	7	2 to 17
Oral misoprostol tablet < 50 µg	0.14	0.04 to 0.32	9	1 to 29
Oral prostaglandins	0.14	0.05 to 0.31	9	1 to 25
Vaginal misoprostol < 50 µg	0.15	0.06 to 0.31	11	4 to 20
Double-balloon or Cook’s catheter	0.15	0.05 to 0.31	9	1 to 24
PGF2 gel	0.16	0.06 to 0.34	14	2 to 28
Oral misoprostol tablet ≥ 50 µg	0.16	0.06 to 0.32	13	6 to 21
Amniotomy	0.16	0.06 to 0.34	13	2 to 29
Laminaria	0.16	0.05 to 0.34	12	1 to 29
Acupuncture	0.16	0.05 to 0.34	13	1 to 28
Vaginal PGE2 (tablet)	0.17	0.07 to 0.33	17	8 to 26
Vaginal PGE2 (gel)	0.17	0.07 to 0.35	18	11 to 24
Intracervical PGE2	0.17	0.06 to 0.34	15	8 to 23
Vaginal misoprostol ≥ 50 µg	0.17	0.07 to 0.34	17	10 to 24
Sustained-release misoprostol vaginal pessary	0.17	0.05 to 0.37	16	1 to 31
i.v. oxytocin with amniotomy	0.17	0.06 to 0.35	17	6 to 28
NO	0.17	0.06 to 0.36	17	5 to 28
Extra-amniotic PGE2	0.17	0.06 to 0.36	15	1 to 30
Titrated (low) oral misoprostol solution	0.18	0.07 to 0.37	19	5 to 30
No intervention	0.19	0.07 to 0.37	21	12 to 28
Vaginal PGE2 pessary (normal release)	0.19	0.07 to 0.38	23	13 to 30
Placebo	0.2	0.08 to 0.38	24	17 to 29
i.v. oxytocin	0.2	0.08 to 0.38	24	18 to 29
Membrane sweeping	0.21	0.08 to 0.41	26	16 to 31
Sexual intercourse	0.22	0.08 to 0.45	25	7 to 32
Relaxin	0.24	0.07 to 0.5	25	4 to 32
Homeopathy	0.24	0.01 to 0.77	18	1 to 32
Mifepristone	0.27	0.1 to 0.52	30	22 to 32
i.v. prostaglandin	0.3	0.1 to 0.58	30	15 to 32

Figure 9 reports the rankograms for instrumental delivery. We note that for all of the interventions the rankograms are flat, with relatively low peaks – indicative of considerable uncertainty around the probability any intervention is the ‘best’. We do not therefore include an assessment of which probability is best in our summary for instrumental delivery.

See Appendix 13 (Table 59) for the results for the sensitivity analysis, excluding trials at high risk of bias. Removing these trials also removed five interventions from the analysis. Consequently, posterior mean ranks appear to have changed (although 95% CrI are overlapping between the two analyses).

Uterine hyperstimulation with fetal heart rate changes

After excluding trials with 0% or 100% events in all arms, 180 trials assessed the outcome of uterine hyperstimulation. The analysis includes 19 interventions, in addition to placebo and no intervention. There were no trials remaining that compared PGF₂, amniotomy, oestrogens, corticosteroids, relaxin, hyaluronidase, membrane sweeping, extra-amniotic PGE₂, i.v. prostaglandin, sexual intercourse, acupuncture, breast stimulation, homeopathy, castor oil or oral prostaglandins (see Figure 5). Model fit statistics were suggestive of inconsistency for this network (see Appendix 11, Table 47). In the first instance, a continuity correction of 0.5 was added to each cell for those studies with zero events in either arm, allowing the log OR to be estimated. This improved the model fit, and the results presented below are based on the continuity corrected REs NMA model assuming consistency.

Table 9 reports the posterior median ORs (95% CrI) for each intervention relative to placebo (the full results for each intervention compared with every other are reported in Appendix 12, Table 53). We note that for all of the interventions the direct and NMA results are similar. Relative to the size of the intervention effect estimates, high to moderate between-trial heterogeneity was observed for this outcome [τ = 0.54 (95% CrI 0.38 to 0.72)]. Figure 8 reports the rankograms for uterine hyperstimulation. The safest intervention in terms of risk of uterine hyperstimulation was double-balloon or Cook’s catheter, with a 47% probability of being the best and a 91% probability of being in the top three interventions.

TABLE 9 - Odds ratios and 95% CrI for uterine hyperstimulation for every intervention compared with placebo

Results were from a single trial with zero events in one arm.

Results from NMA and pairwise meta-analysis (when possible). An OR of > 1 favours placebo (i.e. fewer events occur on a placebo than active intervention). An OR of < 1 favours the active intervention (i.e. fewer undesirable events occurred on the active intervention). Empty cells indicate that direct evidence was not available for that comparison. The column ‘Direct trials’ reports the number of trials available for the direct comparisons vs. placebo only.

Active intervention	NMA		Pairwise meta-analysis
	OR	95% CrI	OR	95% CrI	Direct trials
Double-balloon or Cook’s catheter	0.26	0.00 to 1.18	–	–	0
NO	0.38	0.02 to 1.54	–	–	0
Laminaria	0.52	0.01 to 2.62	–	–	0
Foley catheter	0.92	0.37 to 1.93	–	–	0
Oral misoprostol tablet < 50 µg	1.13	0.28 to 3.15	–	–	0
Vaginal PGE2 pessary (normal release)	1.40	0.37 to 3.68	0.46	0.00 to 3.00	1
Intracervical PGE2	1.70	0.87 to 3.05	1.65	0.57 to 3.88	8
Titrated (low-dose) oral misoprostol solution	1.93	0.73 to 4.19	–	–	0
Vaginal PGE2 (tablet)	1.99	0.78 to 4.25	0.78	0.00 to 5.12	1
i.v. oxytocin	2.12	0.97 to 4.10	0.34	0.00 to 2.19	1
Vaginal PGE2 (gel)	2.33	1.10 to 4.40	5.81	0.32 to 29.93	3
Vaginal misoprostol < 50 µg	2.75	1.36 to 5.04	2.46	0.25 to 10.23	2
Oral misoprostol tablet ≥ 50 µg	2.85	1.41 to 5.20	7.75	1.22 to 30.55	5
Vaginal PGE2 pessary (slow release)	2.97	1.36 to 5.73	27.00	2.01 to 131.2	3
Buccal/sublingual misoprostol	4.25	1.71 to 9.02	–	–	0
Vaginal misoprostol tablet ≥ 50 µg	4.40	2.22 to 7.94	28.54	0.53 to 159.4	2
Sustained-release misoprostol vaginal pessary	5.58	1.58 to 14.57	–	–	0
i.v. oxytocin with amniotomy	7.44	0.27 to 40.66	–	–	0
Mifepristonea	Not estimable		Not estimable		1

Table 10 reports the posterior mean ranks and absolute probabilities for this outcome. The mean rank for double-balloon or Cook’s catheter was ‘2’, with a 95% CrI ranging from 1 to 7 (of 19 interventions). Double-balloon or Cook’s catheter also had the lowest absolute probability of hyperstimulation at 1% (95% CrI 0% to 3%). The probability of being ranked in the bottom three (i.e. intervention with highest risk of uterine hyperstimulation) was 64% for sustained-release misoprostol insert and 59% for vaginal misoprostol (≥ 50 µg). The intervention with the worst mean rank was vaginal misoprostol ≥ 50 µg: mean rank 19 (95% CrI 17 to 21). The absolute probability of uterine hyperstimulation for vaginal misoprostol ≥ 50 µg was 9% (95% CrI 2% to 25%).

TABLE 10 - Absolute probability of uterine hyperstimulation across all 19 interventions and placebo/no intervention included in the NMA. Posterior mean rank and 95% CrIs

Intervention	Absolute probability of hyperstimulation		Posterior mean rank and 95% CrI
	Posterior mean	95% CrI
Double-balloon or Cook’s catheter	0.01	0.00 to 0.03	2	1 to 6
NO	0.01	0.00 to 0.04	3	1 to 8
Laminaria	0.01	0.00 to 0.06	3	1 to 13
Foley catheter	0.02	0.00 to 0.07	5	3 to 9
Placebo	0.02	0.00 to 0.08	6	3 to 10
Oral misoprostol tablet < 50 µg	0.03	0.00 to 0.09	6	2 to 15
Vaginal PGE2 pessary (normal release)	0.03	0.00 to 0.11	8	3 to 16
No treatment	0.03	0.00 to 0.12	8	3 to 17
Intracervical PGE2	0.04	0.01 to 0.12	10	6 to 13
Vaginal PGE2 (tablet)	0.04	0.01 to 0.11	11	6 to 17
Titrated (low-dose) oral misoprostol solution	0.04	0.01 to 0.14	11	5 to 17
i.v. oxytocin	0.05	0.01 to 0.14	12	7 to 17
Vaginal PGE2 (gel)	0.05	0.01 to 0.15	13	9 to 17
Vaginal misoprostol < 50 µg	0.06	0.01 to 0.18	15	11 to 18
Oral misoprostol tablet ≥ 50 µg	0.06	0.01 to 0.18	15	11 to 18
Vaginal PGE2 pessary (slow release)	0.06	0.01 to 0.19	15	10 to 19
Buccal/sublingual misoprostol	0.09	0.02 to 0.26	19	13 to 21
Vaginal misoprostol ≥ 50 µg	0.09	0.02 to 0.25	19	17 to 21
Sustained-release misoprostol vaginal pessary	0.11	0.02 to 0.34	18	10 to 21
i.v. oxytocin with amniotomy	0.11	0.00 to 0.52	14	3 to 21
Mifepristone	0.26	0.01 to 0.89	19	7 to 21

Results were largely robust to the pre-planned sensitivity analysis based on allocation concealment bias. The posterior mean rank for sustained-release misoprostol insert changed from 18 (95% CrI 11 to 21) to 11 (95% CrI 3 to 19). Full sensitivity analysis results are reported in Appendix 13, Table 57.

Neonatal and maternal mortality and severe morbidity

It was not possible to conduct a NMA for composite outcomes of neonatal mortality and serious morbidity or maternal mortality and serious morbidity, as these were too rare or poorly reported to carry out meaningful analysis. The full data sets for these outcomes are reported in Appendix 14 (Tables 64 and 65). In addition, there is a lack of a universally accepted definition for serious infant or maternal morbidity. Although we planned to include any such reported outcome by individual trials, the outcomes were still rarely reported. Only 21.3% of included trials (131/611) reported perinatal deaths with an incidence of 0.3% (94/32,248). A total of 77 out of 611 trials (12.6%) reported a total of 20 maternal deaths or serious morbidity [five deaths, 14 uterine ruptures and one intensive care unit (ICU) admission for infection], that is, an incidence of 0.1%. For completeness, we included the network diagrams for both outcomes (Figures 10 and 11). The network diagram includes those trials reporting at least one event (42 of the included trials reported at least one perinatal death and 16 trials reported at least one case of maternal death or severe morbidity).

FIGURE 10.

Neonatal mortality. Network diagram of studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, PGF₂ gel; 7, intracervical PGE₂; 8, vaginal PGE₂ pessary (normal release); 9, vaginal misoprostol (dose < 50 µg); 10, vaginal misoprostol (dose ≥ 50 µg); 11, oral misoprostol tablet (dose ≥ 50 µg); 12, titrated (low-dose) oral misoprostol solution; 13, i.v. oxytocin; 14, i.v. oxytocin with amniotomy; 15, NO; 16, Foley catheter; 17, laminaria; 18, membrane sweeping; 19, extra-amniotic PGE₂; 20, i.v. prostaglandin; 21, sexual intercourse; 22, breast stimulation; 23, oral prostaglandins; 24, buccal/sublingual misoprostol.

FIGURE 11.

Maternal mortality and serious morbidity. Network diagram of studies included in analysis. The width of the lines is proportional to the number of trials directly comparing each pair of interventions. The size of each node is proportional to the number of randomised participants (sample size). 1, no intervention; 2, placebo; 3, vaginal PGE₂ (tablet); 4, vaginal PGE₂ (gel); 5, vaginal PGE₂ pessary (slow release); 6, intracervical PGE₂; 7, vaginal PGE₂ pessary (normal release); 8, vaginal misoprostol (dose < 50 µg); 9, vaginal misoprostol (dose ≥ 50 µg); 10, oral misoprostol tablet (dose ≥ 50 µg); 11, i.v. oxytocin; 12, i.v. oxytocin with amniotomy; 13, mifepristone; 14, mechanical methods – Foley catheter; 15, mechanical methods – laminaria; 16, buccal/sublingual misoprostol.

Neonatal intensive care unit admission

After the exclusion of trials with 0% or 100% events in all arms, 205 trials assessed the outcome of admission to the NICU and the network is shown in Figure 6. There were no trials remaining that compared corticosteroids, relaxin, hyaluronidase, i.v. prostaglandin, breast stimulation, homeopathy or castor oil. Model fit statistics indicated evidence of inconsistency for this network, with the inconsistency model resulting in a considerable decrease in between-trial heterogeneity (see Appendix 11, Table 49). Comparing the NMA estimates with those from the pairwise analysis identified 23 intervention comparisons for which the NMA and direct evidence were in disagreement. A further investigation of this apparent inconsistency was conducted using a ‘node-splitting’ approach. 942 Node splitting separates evidence on a particular comparison (node) into direct and indirect to identify how the indirect evidence was combining with, or adding to, the direct evidence to form the NMA estimates. Using this approach, 3 out of 23 comparisons were highlighted as having significant differences in the contribution of the direct and indirect evidence to the NMA estimate. The three comparisons were vaginal misoprostol (≥ 50 µg) against NO, vaginal PGE₂ pessary (slow release) against titrated (low-dose) oral misoprostol solution, and no treatment against oral misoprostol tablet (≥ 50 µg). The first two of these were identified as being a consequence of zero cells in the direct evidence estimating a very extreme treatment effect. However, the remaining comparison between no treatment and oral misoprostol tablet (≥ 50 µg) had statistically significant differences in the direct and indirect evidence (Bayesian p-value = 2.98401E-05), even when trials with zero cells were removed.

Within the no treatment against oral misoprostol tablet (≥ 50 µg) comparison, one trial in particular, Rath and Manus,701 was identified as deviant from the rest of the evidence and was therefore re-examined. The criteria for admission to the NICU in this study were unclear, and the description of the facility was given simply as ‘nursery’. A post hoc decision to remove this trial for this outcome was taken and a further analysis was subsequently carried out. The REs model, excluding the Rath and Manus trial701 and assuming consistency, was a good fit to the data, and the results presented here are therefore from this analysis.

Table 11 reports the posterior median ORs (95% CrI) for each intervention relative to placebo (full results are reported in Appendix 12, Table 55). Relative to the size of the intervention effect estimates, moderate between-trial heterogeneity was observed for this outcome [τ = 0.17 (95% CrI 0.04 to 0.30)]. Using placebo as the reference only, extra-amniotic PGE₂ resulted in significant reduction in NICU admission. Table 12 reports the posterior mean ranks for NICU admission. Extra-amniotic PGE₂ had the best mean rank of all interventions (4), with a 95% CrI ranging from 1 to 15. This intervention also had the lowest absolute probability of NICU admission at 4% (95% CrI 0.6% to 12%) and a 59% chance of being in the top three interventions.

TABLE 11 - Odds ratios and 95% CrI for NICU admission for every intervention compared with placebo

Data from a single trial with zero events in one arm.

Results from NMA and pairwise meta-analysis (when possible). An OR of > 1 favours placebo (i.e. fewer events occur on a placebo than active intervention). An OR of < 1 favours the active intervention (i.e. fewer undesirable events occurred on the active intervention). Empty cells indicate that direct evidence was not available for that comparison. The column ‘trials’ reports the number of trials available for the direct comparisons vs. placebo only.

Active intervention vs. placebo	NMA		Pairwise meta-analysis
	OR	95% CrI	OR	95% CrI	Trials
Extra-amniotic PGE2	0.40	0.16 to 0.82	–	–	0
Sexual intercourse	0.48	0.14 to 1.17	–	–	0
PGF2 gel	0.56	0.18 to 1.36	–	–	0
Sustained-release misoprostol vaginal pessary	0.59	0.31 to 1.03	–	–	0
Double-balloon or Cook’s catheter	0.60	0.26 to 1.15	–	–	0
Foley catheter	0.66	0.41 to 1.00	–	–	0
Titrated (low-dose) oral misoprostol solution	0.67	0.39 to 1.07	–	–	0
Oral prostaglandins	0.68	0.09 to 2.40	–	–	0
Vaginal PGE2 pessary (slow release)	0.73	0.44 to 1.11	29.03	0.45 to 156.3	1
Buccal/sublingual misoprostol	0.73	0.42 to 1.19	–	–	0
Vaginal misoprostol < 50 µg	0.74	0.49 to 1.06	0.95	0.38 to 1.94	2
Intracervical PGE2	0.76	0.48 to 1.12	1.06	0.08 to 4.41	2
i.v. oxytocin	0.76	0.50 to 1.12	0.78	0.06 to 3.02	1
Oral misoprostol tablet < 50 µg	0.79	0.31 to 1.63	–	–	0
NO	0.82	0.54 to 1.20	0.92	0.56 to 1.43	5
Vaginal PGE2 (tablet)	0.83	0.42 to 1.44	–	–	0
Oral misoprostol tablet ≥ 50 µg	0.83	0.55 to 1.20	0.75	0.28 to 1.61	3
Membrane sweeping	0.83	0.43 to 1.46	1.14	0.01 to 6.19	1
Amniotomy	0.84	0.22 to 2.26	–	–	0
Vaginal misoprostol ≥ 50 µg	0.85	0.57 to 1.23	–	–	0
Vaginal PGE2 (gel)	0.88	0.59 to 1.26	0.71	0.26 to 1.58	4
Vaginal PGE2 pessary (normal release)	0.88	0.51 to 1.40	0.86	0.30 to 1.94	3
Acupuncture	0.94	0.11 to 3.36	1.43	0.13 to 5.95	2
Oestrogens	1.43	0.01 to 7.80	2.29	0.02 to 12.21	1
Laminaria	1.54	0.40 to 4.31	–	–	0
i.v. oxytocin with amniotomy	1.60	0.71 to 3.06	–	–	0
Mifepristonea	1.71	0.73 to 3.55	1.15	0.38 to 2.75	1

TABLE 12 - Absolute probability of NICU admission across all 27 interventions and placebo/no intervention included in the NMA

Intervention	Absolute probability of NICU admission		Posterior mean rank and 95% CrI
	Posterior mean	95% CrI
Extra-amniotic PGE2	0.04	0.01 to 0.12	4	1 to 15
Sexual intercourse	0.04	0.01 to 0.14	6	1 to 25
PGF2 gel	0.05	0.01 to 0.16	8	1 to 26
Sustained-release misoprostol vaginal pessary	0.05	0.01 to 0.15	8	2 to 22
Double-balloon or Cook’s catheter	0.05	0.01 to 0.16	9	2 to 25
Vaginal PGE2 pessary (slow release)	0.06	0.01 to 0.18	13	6 to 23
Intracervical PGE2	0.06	0.01 to 0.18	14	7 to 23
Vaginal misoprostol < 50 µg	0.06	0.01 to 0.18	13	7 to 20
Titrated (low-dose) oral misoprostol solution	0.06	0.01 to 0.17	11	4 to 22
i.v. oxytocin	0.06	0.01 to 0.18	15	8 to 22
Foley catheter	0.06	0.01 to 0.16	10	5 to 19
Oral prostaglandins	0.06	0.00 to 0.23	10	1 to 29
Buccal/sublingual misoprostol	0.06	0.01 to 0.18	13	4 to 25
Vaginal PGE2 (tablet)	0.07	0.02 to 0.17	16	4 to 27
Vaginal PGE2 (gel)	0.07	0.02 to 0.20	20	13 to 25
Vaginal PGE2 pessary (normal release)	0.07	0.02 to 0.21	18	6 to 27
Vaginal misoprostol ≥ 50 µg	0.07	0.02 to 0.20	19	12 to 25
Oral misoprostol tablet < 50 µg	0.07	0.01 to 0.20	14	2 to 28
Oral misoprostol tablet ≥ 50 µg	0.07	0.02 to 0.19	18	10 to 24
Amniotomy	0.07	0.01 to 0.23	14	1 to 29
NO	0.07	0.01 to 0.20	17	5 to 26
Membrane sweeping	0.07	0.01 to 0.20	16	5 to 27
Placebo	0.08	0.02 to 0.23	23	16 to 27
No intervention	0.08	0.02 to 0.22	23	13 to 28
Acupuncture	0.08	0.00 to 0.32	14	1 to 29
Oestrogens	0.10	0.00 to 0.53	14	1 to 29
i.v. oxytocin with amniotomy	0.12	0.02 to 0.33	27	17 to 29
Laminaria	0.12	0.02 to 0.37	23	4 to 29
Mifepristone	0.13	0.02 to 0.37	26	13 to 29

Figure 12 reports the rankograms for NICU admission. For all interventions the rankograms are flat and indicative of considerable uncertainty around the probability any intervention is the ‘best’. We do not therefore include an assessment of which probability is ‘best’ in our summary for this outcome as it would be misleading.

FIGURE 12.

Rankograms for each of the 29 induction interventions for Apgar score < 7 at 5 minutes and NICU admission. Ranking indicates the probability of being the best intervention, the second best, the third best, etc. The x-axis shows the relative ranking and the y-axis the probability of each ranking. (a) No treatment; (b) placebo; (c) vaginal PGE₂ (tablet); (d) vaginal PGE₂ (gel); (e) vaginal PGE₂ pessary (slow release); (f) PGF₂ gel; (g) intracervical PGE₂; (h) vaginal pessary (normal release); (i) vaginal misoprostol (dose < 50 µg); (j) vaginal misoprostol (dose ≥ 50 µg); (k) oral misoprostol (dose < 50 µg); (l) oral misoprostol (dose ≥ 50 µg); (m) titrated (low-dose) oral misoprostol solution; (n) sustained-release misoprostol insert; (o) i.v. oxytocin; (p) amniotomy; (q) i.v. oxytocin plus amniotomy; (r) NO; (s) mifepristone; (t) oestrogens; (u) Foley catheter; (v) laminaria including dilapan; (w) double balloon or Cook’s catheter; (x) membrane sweeping; (y) extra-amniotic PGE₂; (z) sexual intercourse; (aa) acupuncture; (ab) oral prostaglandins; and (ac) buccal/sublingual misoprostol.

All results were robust to the preplanned sensitivity analysis excluding studies at high risk of bias for allocation concealment and are reported in Appendix 13, Table 58.

Apgar score < 7 at 5 minutes

After the exclusion of trials with 0% or 100% events in all arms, 200 trials of 28 interventions assessed the outcome of Apgar score < 7 at 5 minutes (see Figure 7). There were no trials remaining that compared PGF₂ gel, oestrogens, corticosteroids, relaxin, hyaluronidase, breast stimulation, homeopathy or castor oil. Residual deviance statistics, for the model assuming consistency, suggested a lack of fit, with the model assuming inconsistency also having slightly lower heterogeneity. Further investigation indicated that this was due to the number of zero events in trial arms rather than heterogeneity in study design. The REs NMA model assuming consistency was therefore the preferred model and reported results are based on this.

Table 13 reports posterior mean ORs (95% CrI) for each intervention relative to placebo (full results are reported in Appendix 12, Table 54). Relative to the size of the intervention effect estimates, moderate to small between-trial heterogeneity was observed for this outcome [τ = 0.19 (95% CrI 0.01 to 0.46)]. Using placebo as the reference intervention, only two interventions resulted in significant reduction in Apgar score < 7 at 5 minutes: NO and buccal/sublingual misoprostol.

TABLE 13 - Odds ratios and 95% CrI for Apgar score < 7 at 5 minutes for every intervention compared with placebo

Not estimable because of comparison being based on a single trial with zero cells and connected to the network on a spur.

Results from NMA and pairwise meta-analysis (when possible). An OR of > 1 favours placebo (i.e. fewer events occur on a placebo than active intervention). An OR of < 1 favours the active intervention (i.e. fewer undesirable events occurred on the active intervention). Empty cells indicate that direct evidence was not available for that comparison.

Active intervention vs. placebo	NMA		Pairwise meta-analysis
	OR	95% CrI	OR	95% CrI	Trials
Extra-amniotic PGE2	Not estimablea		–	–	0
Double-balloon or Cook’s catheter	0.17	0.01 to 1.67	–	–	0
Oral prostaglandins	0.35	0.06 to 1.68	–	–	0
Buccal/sublingual misoprostol	0.41	0.15 to 0.99	–	–	0
Titrated (low) oral misoprostol solution	0.46	0.19 to 1.09	–	–	0
NO	0.49	0.20 to 0.95	0.94	0.39 to 1.88	5
Oral misoprostol tablet < 50 µg	0.53	0.13 to 2.08	–	–	0
Acupuncture	0.54	0.14 to 1.87	0.82	0.15 to 2.49	3
Oral misoprostol tablet ≥ 50 µg	0.57	0.30 to 1.13	0.85	0.18 to 2.41	3
Intracervical PGE2	0.67	0.38 to 1.20	0.46	0.14 to 1.11	4
Vaginal PGE2 (tablet)	0.75	0.34 to 1.62	0.57	0.04 to 2.04	1
Mifepristone	0.77	0.23 to 3.37	0.78	0.16 to 2.59	2
Vaginal PGE2 pessary (normal release)	0.80	0.35 to 1.84	1.79	0.11 to 8.27	4
Foley catheter	0.82	0.41 to 1.65	–	–	0
i.v. oxytocin	0.85	0.45 to 1.62	Not estimable
Vaginal misoprostol < 50 µg	0.92	0.49 to 1.69	0.04	0 to 0.32	1
Laminaria	0.92	0.25 to 3.41	–	–	0
Sexual intercourse	0.97	0.02 to 37.3	–	–	0
Vaginal misoprostol ≥ 50 µg	1.01	0.56 to 1.81	–	–	0
Vaginal PGE2 (gel)	1.03	0.58 to 1.85	0.70	0.12 to 2.21	5
Vaginal PGE2 pessary (slow release)	1.06	0.43 to 2.60	–	–	0
i.v. prostaglandin	1.12	0.29 to 4.25	–	–	0
Amniotomy	1.30	0.37 to 4.61	–	–	0
Membrane sweeping	1.85	0.63 to 5.40	–	–	0
Sustained-release misoprostol vaginal pessary	1.91	0.57 to 6.35	–	–	0
i.v. oxytocin with amniotomy	2.39	0.62 to 9.58	–	–	0

Table 14 reports the absolute probabilities and posterior mean ranks for each intervention. The safest intervention in terms of risk of Apgar score < 7 at 5 minutes was double-balloon or Cook’s catheter, with a mean rank of ‘4’; however, the 95% CrI ranged from ‘1’ to ‘22’ out of 28 interventions, reflecting the considerable uncertainty in this estimate. Double-balloon or Cook’s catheter also had the lowest absolute probability of an event at 1.1% (CrI 0.02% to 6.5%). Buccal/sublingual misoprostol had a posterior mean rank of ‘5’ (95% CrI 1 to 15) and an absolute probability of Apgar score < 7 at 5 minutes of 1.4% (95% CrI 0.2% to 5%).

TABLE 14 - Absolute probability of Apgar score < 7 at 5 minutes across all 26 interventions and placebo/no intervention included in the NMA

Single trial with zero events in one arm.

Intervention	Absolute probability of Apgar score < 7 at 5 minutes admission		Posterior mean rank and 95% CrI
	Posterior mean	95% CrI
Double-balloon or Cook’s catheter	0.01	0.00 to 0.06	4	1 to 22
Oral prostaglandins	0.01	0.00 to 0.07	7	1 to 24
Buccal/sublingual misoprostol	0.01	0.00 to 0.05	5	1 to 15
Vaginal PGE2 (tablet)	0.02	0.00 to 0.07	12	3 to 23
Intracervical PGE2	0.02	0.00 to 0.07	10	5 to 16
Oral misoprostol tablet < 50 µg	0.02	0.00 to 0.08	9	1 to 24
Oral misoprostol tablet ≥ 50 µg	0.02	0.00 to 0.06	8	3 to 15
Titrated (low) oral misoprostol solution	0.02	0.00 to 0.06	7	2 to 17
NO	0.02	0.00 to 0.06	7	2 to 17
Acupuncture	0.02	0.00 to 0.09	9	1 to 25
Placebo	0.03	0.01 to 0.1	17	10 to 23
No intervention	0.03	0.00 to 0.11	17	7 to 25
Vaginal PGE2 (gel)	0.03	0.01 to 0.1	19	12 to 23
Vaginal PGE2 pessary (normal release)	0.03	0.00 to 0.10	13	4 to 24
Vaginal misoprostol < 50 µg	0.03	0.00 to 0.10	16	9 to 23
Vaginal misoprostol ≥ 50 µg	0.03	0.01 to 0.10	18	11 to 23
i.v. oxytocin	0.03	0.00 to 0.09	15	8 to 21
Mifepristone	0.03	0.00 to 0.13	14	2 to 27
Foley catheter	0.03	0.00 to 0.09	14	7 to 22
Laminaria	0.03	0.00 to 0.13	16	2 to 27
Vaginal PGE2 pessary (slow release)	0.04	0.01 to 0.12	18	7 to 25
i.v. prostaglandin	0.04	0.00 to 0.16	18	3 to 27
Amniotomy	0.05	0.00 to 0.18	20	4 to 27
Membrane sweeping	0.06	0.01 to 0.21	23	12 to 27
Sustained-release misoprostol vaginal pessary	0.07	0.01 to 0.24	24	10 to 27
i.v. oxytocin with amniotomy	0.08	0.01 to 0.29	24	12 to 27
Sexual intercourse	0.08	0.00 to 0.59	15	1 to 27
Extra-amniotic PGE2a	Not estimable

Table 14 also reports that three further interventions had a posterior mean rank of ‘7’: titrated (low-dose) oral misoprostol solution, NO and oral prostaglandins. However, the uncertainty around these rankings is considerable. Low ranking interventions include i.v. oxytocin with amniotomy, misoprostol vaginal pessary (sustained release) and membrane sweeping. Note that the ORs relative to placebo did not achieve statistical significance for any of these interventions (see Table 13).

Figure 12 reports the rankograms for Apgar score < 7 at 5 minutes. For all of the interventions the rankograms are flat and indicative of considerable uncertainty around the probability that any intervention is the ‘best’. Therefore, we did not include an assessment of probability for being the ‘best’ in our summary for this outcome.

Maternal satisfaction with care and induction of labour method

Less than 5% of the studies included in the review reported data relating to maternal satisfaction with the induction process. In Table 15 we set out findings from these trials. We were unable to pool any results from trials in either pairwise or NMA. The trials focused on a broad range of interventions (10/29 examined oxytocin) and comparators. Furthermore, outcome definitions varied considerably. For mechanical methods, the questions related to discomfort during the initial procedure (e.g. insertion of catheter or membrane sweeping). For other methods there were more global assessments of the process. There were no preferred methods and, in general, women were satisfied with (or at least accepted) the induction process.

TABLE 15 - Maternal satisfaction with the method of induction

ID, identification; NC, not clear.

Study ID	Intervention	Comparison	Satisfaction outcomes	Results	Notes
Adeniji 200551	Vaginal misoprostol 50 µg (n = 50)	Foley catheter (n = 46)	Maternal discomfort (NC). Maternal questionnaires	Intravaginal Misoprostol was well received by the patients . . . showing 85% acceptance of Misoprostol with average expression of minimal discomfort at insertion, in contrast to 35% acceptance, moderate discomfort and resentment of ‘something between thighs’ in the Foley catheters group (p < 0.05)	Study in Nigeria, 2003. It was not clear when women completed questionnaires or how outcomes were measured. The number of women responding to questionnaires was not stated
Ashrafunnessa 199773	Intracervical PGE2 gel 500 µg (n = 49)	i.v. oxytocin (n = 49)	Women’s opinions regarding acceptability of methods (rated recommendable, acceptable, unsatisfactory or no answer)	Intracervical PGE2: 16/49 rated as recommendable, 17/49 acceptable, 11/49 unsatisfactory and 5/49 no answer i.v. oxytocin: 22/49 rated as recommendable, 19/49 acceptable, 4/49 unsatisfactory and 4/49 no answer	Study in India; not clear when the study was carried out. It was not clear when women were asked about their opinions. It was stated that there was no significant difference between groups for rating of labour induction method
Bollapragada 2009107	Self-administered at home NO donor (ISMN) (n = 177)	Placebo (n = 173)	Women’s experience of induction of labour; pain and anxiety Outcomes measured on admission to hospital Discomfort and anxiety measured on a 10-point scale General satisfaction measured post delivery; six questions Likert scale 1–10 (1 best)	Maternal satisfaction outcomes mean scores and SD: Labour [from very easy (1) to very difficult (10)]. ISMN 6.18 (2.46) vs. placebo 6.52 (2.16) (p = 0.26) Experience of taking tablets (1 extremely good, 10 not at all good). ISMN 3.84 (2.3) vs. placebo 3.23 (2.15) (p = 0.043) Pain (1 not at all painful, 10 very painful). ISMN 2.76 (2.3) vs. placebo 2.18 (2.18) (p = 0.056) Anxiety (1 not at all anxious, 10 very anxious). ISMN 2.5 (1.96) vs. placebo 2.39 (1.88) (p = 0.67) Same treatment again (1 definitely, 10 definitely not). ISMN 3.39 (2.74) vs. placebo 2.77 (2.19) (p = 0.063) Advise friend to have same (1 definitely, 10 definitely not). ISMN 3.1 (2.38) vs. placebo 2.69 (2.07) (p = 0.17)	Study in UK. Response rates for satisfaction outcomes approximately 63%. Overall, most women expressed positive views about home treatment. Women in the placebo group had slightly more positive views, and women in the ISMN group who suffered headache had significantly fewer positive views (data not shown)
Boulvain 1998110	Membrane sweep (n = 99)	No treatment (vaginal examination only) (n = 99)	Pain following first visit and 24 hours later VAS Women who had membrane sweep were asked for views postpartum	Mean pain score during initial vaginal examination/membrane sweep: sweep group 2.4 (1.3–4.3), control 1.5 (0.4–3.4) (p = 0.001) Postpartum women who had had membrane sweep: 86.7% said they would recommend the intervention; some women described the procedure as unpleasant 31%	Study in Canada 1995–6; response rates to pain questionnaire 87%
Bullarbo 2007122	NO donor (ISMN) (n = 100)	Placebo (n = 100)	Opinion of outpatient procedure and whether or not women would recommend this treatment	Most women in both groups were either positive or very positive to the treatment. Eighty-nine of the women (94.7%) in the isosorbide mononitrate group and 93 of the women (93.9%) in the placebo group reported that they would recommend the procedure	Study in Sweden; 94% of women in intervention group and 99% controls responded
De Miranda 2006201	Membrane sweep (n = 375)	No intervention (n = 367)	Pain and whether or not women would choose the same procedure again	Women who had undergone membrane sweep – report: 51% thought membrane sweep was somewhat painful and 17% painful or very painful; after delivery 88% said that they would choose a membrane sweep in a subsequent pregnancy	The Netherlands, 2000–3; 94% in the intervention group responded to the postpartum survey of views
Gribel 2011314	Acupuncture (n = 35)	Vaginal misoprostol 25 µg (n = 32)	Satisfaction with the labour induction technique. It was not clear how satisfaction outcomes were measured	Satisfaction with the technique was informed by patients in group (acupuncture) 89% and M (misoprostol) 69% with significant difference between groups	Study in Brazil 2007–9
Güngördük 2012319	i.v. oxytocin (n = 221)	Sustained-release PGE2 (0.3 mg/hour) (n = 223)	Maternal satisfaction with childbirth experience and pain VAS scale 0–10, higher scores greater satisfaction, and worse pain. Reported within 24 hours of the birth	VAS for satisfaction with birth process (higher scores = better) i.v. oxytocin 8.1 (1.14) vs. PGE2 8.08 (0.6) (p = 0.88) Pain (higher scores = worse) oxytocin 5.16 (2.4) vs. PGE2 4.07 (1.68) (p < 0.001) (oxytocin more painful)	Study in Turkey 2009–10
Hannah 1996335	Immediate induction of labour with i.v. oxytocin (n = 1258) or PGE2 vaginal gel (n = 1259)	Expectant management (n = 2524)	Women’s evaluations of care	Compared with expectant management, fewer women in the oxytocin reported that there was nothing that they liked about their treatment (13.7% vs. 5.9%) and more women in the oxytocin group said they would participate in the study again (59.9% vs. 67.3%) Compared with expectant management, fewer women in the PGE2 group reported that there was nothing that they liked about their treatment (11.7% vs. 5.1%) and more women in the PGE2 group said that they would participate in the study again (59.2% vs. 66.5%) It was reported that there were no significant differences between groups for other measures of maternal satisfaction	Multicentre study in Canada, UK, Australia, Israel, Sweden and Denmark Women recruited between 1992 and 1995
Kennedy 1978419	i.v. oxytocin with amniotomy (n = 27)	Intracervical PGE2 (n = 28)	Maternal reactions to method (favourable vs. unfavourable) and whether labour was better or worse than previous labours (for multiparous women only)	Reaction unfavourable: 1/27 oxytocin, 1/27 cervical PGE2 gel Labour worse than previous ones: 2/11 oxytocin, 2/14 cervical PGE2	UK study. Brief report. Most women 55/60 responded to survey but data on experience of labour for multiparous women only
Kennedy 1982420	Vaginal PGE2 tablet (n = 50)	i.v. oxytocin with amniotomy (n = 50)	Maternal reactions to method (favourable vs. unfavourable)	Reaction unfavourable: PGE2 0/50, oxytocin with amniotomy 26/50	Study carried out in the UK
Legarth 1987460	Vaginal PGE2 pessary 2.5 mg (n = 49)	i.v. oxytocin (n = 49)	Women’s perceptions of pain and view of method of induction used	In the PGE2 group, 19/47 reported intense pain vs. 11/45 in the oxytocin group The method was reported as unsatisfactory by 1/47 in the PGE2 group and 7/45 in the oxytocin group	Study in Denmark
Lo 1994480	Vaginal PGE2 tablet (n = 101)	i.v. oxytocin (n = 99)	Maternal acceptance of method It was not clear what women were asked	Method rated positively by 77/99 in the oxytocin group and 63/101 in the PGE2 group	Study in Hong Kong 1991–2; results stratified by parity
Lyndrup 1990494	Vaginal PGE2 pessary 2.5 mg (n = 43)	i.v. oxytocin (n = 48)	Women’s comments (method recommendable, acceptable or unsatisfactory)	In the PGE2 group, 3/29 described the method as unsatisfactory compared with 8/32 in the oxytocin group (p = 0.001)	Study in Denmark over 3 years
Mei-Dan 2012553	Foley catheter (n = 88)	Double-balloon catheter (Cook) (n = 100)	Pain perception during insertion rated on a 1–10 scale (higher score worse)	Mean pain score Foley catheter group 3.3 (2.3) vs. double-balloon catheter 3.4 (2.3) p = 0.77	Study in Israel
Nassar 2006595	Vaginal misoprostol 50 µg (n = 85)	Sublingual misoprostol 50 µg (n = 85)	Questionnaire completed following the birth including questions on induction method	In the vaginal misoprostol group, 18/72 said that they would opt for the same route in any subsequent induction vs. 59/76 in the sublingual route In the vaginal misoprostol group, 27/72 reported that they would have a favourable view of induction in a future pregnancy compared with 46/76 in the sublingual group	Study in Beirut 2004–6
Paul 1992652	i.v. oxytocin (n = 20)	Oral PGE2 (n = 15)	Women’s view of method (favourable, non-committal, unfavourable)	In the oxytocin group, 13/20 had an unfavourable opinion compared with none in the PGE2 group
Shetty 2002780	Oral misoprostol 50 µg (n = 50)	Sublingual misoprostol 5 µg (n = 50)	Not clear how satisfaction was measured	It was reported that satisfaction rates were 82.5% and 85.7% in the oral and sublingual groups, respectively	UK study 2000; 82% returned postnatal questionnaires
Shetty 2002784	Oral misoprostol 50 µg (n = 124)	Sublingual misoprostol 5 µg (n = 125)	Brief satisfaction questionnaire about satisfaction and preferences for the future	High levels of satisfaction with induction method in both groups (87–88%)	UK study 2000–1; 78% of women responded to satisfaction questionnaire
Surita 2005826	Foley catheter (n = 70)	Hyaluronidase (n = 70)	Women reported satisfaction with and discomfort associated with each method	In the Foley catheter group, 56/70 were satisfied, and 12/70 reported that the method was very or relatively uncomfortable In the hyaluronidase group, 49/70 were satisfied and 10/70 were very or relatively uncomfortable	Study in Brazil 2000–2
Tan 2013837	i.v. oxytocin (105)	Placebo (101)	Satisfaction with the birth process on a 1–10 scale (lower score better) 24 hours after the birth	i.v. oxytocin mean score 3 (3–4), placebo 3 (3–5) p = 0.36	Study in Malaysia 2010–12
Cardozo 1986137	PGE2 vaginal pessary 3 mg (n = 195)	Expectant management (n = 207)	Satisfaction with management (pleased, no comment, disappointed)	In the PGE2 group, 97/195 reported that they were pleased with their management compared with 110/207 in the expectant management group	Study in UK
Colon 2005173	Vaginal misoprostol 25 µg (n = 111)	Oral misoprostol 50 µg (n = 93)	Not clear how satisfaction was measured post delivery	Ninety-eight per cent of women in both groups expressed satisfaction with their overall experience in hospital; 14% of vaginal group vs. 7.5% in oral group were dissatisfied with the use of misoprostol	Study in USA; 153/204 responded to survey
Dodd 2006214	Oral misoprostol solution 20 µg (n = 365)	Vaginal PGE2 gel (n = 376)	Women’s preferences	Overall 58.5% said that that they would prefer an oral induction agentWomen in the misoprostol group were more likely to say they ‘liked everything’ with their labour and birth	Study in Australia
Ferraiolo 2010258	PGE2 vaginal gel 1 mg (n = 72)	PGE2 vaginal pessary (sustained release) 10 mg (n = 79)	Pre and post delivery maternal questionnaires	It was reported that in the post-induction questionnaires there was no significant difference in anxiety (p = 0.073) or discomfort (0.073). A burning sensation on application was experienced by 31.9% of women in the vaginal gel group and 26.6% in the sustained-release pessary group	Study in Italy 2007–8; 173 recruited but 22 excluded as they did not complete questionnaires or did not complete them correctly
Girija 2009293	Vaginal misoprostol 25 µg (n = 50)	Vaginal misoprostol 50 µg (n = 50)	Not clear when or how satisfaction was measured	Eighty percent (22/25) women in the 25 µg group and 100% 23/23 of women in the 50 µg group had a satisfaction level of more than 50% (p = 0.23)	Study in India 2004–5; data on satisfaction available for only 48/100 randomised
Girija 2011294	Vaginal misoprostol 25 µg (n = 159)	PGE2 gel 0.5 mg, intracervical (n = 161)	Not clear how or when satisfaction was measured	More than 50% satisfaction of (sic) was observed in 107 (89.2%) mothers in misoprostol group and 109 (91.6%) which was not statistically significant p = 0.6762	Study in India 2006–8; 239/320 responded to satisfaction questionnaire
Tomlinson 2001856	PGE2 vaginal gel 1–2 mg (n = 34)	PGE2 vaginal pessary (sustained release) (n = 35)	Outcomes measured on a Likert scale	Pain on insertion: 2.7 (0–8) in the PGE2 gel group compared with 3.0 (0–10) in the sustained-release pessary group (difference not significant) Satisfaction with induction score: 3.9 (1–6) in the PGE2 gel group and 4.3 (1–6) in the sustained-release pessary group (not significant)	Study in UK
Van Gemund 2004879	1 mg of vaginal PGE2 gel (n = 340)	25 µg of misoprostol vaginal (n = 341)	Preference for subsequent labour	In the PGE2 gel group, 164/286 would choose the same method again compared with 179/291 in the misoprostol group	Study in the Netherlands

Chapter 4 Assessment of cost-effectiveness

Health-economic model

A decision-analytic model956 was constructed to compare the costs and effects of the different methods of induction of labour. Because we consider only short-term consequences, we chose to use a decision tree to represent the costs and consequences of different methods of induction. A decision tree is a graphical representation of different possible outcomes following a decision, in which probabilities are given to different paths along the branches of the tree, and costs and utilities attached to each branch. This enables us to compute probability-weighted costs and outcomes to arrive at an expected cost and utility value for each alternative treatment option.

The outcomes included were rate of VD within 24 hours, CS rate and frequency of admission to the NICU, as well as resource use and utilities. This structure was informed by the literature and expert opinion, and was finalised through discussions with the steering group. An illustration of the model structure is provided in Figure 13. Squares represent decision nodes for the method of delivery chosen, whereas circles represent chance nodes at which different possible outcomes are assigned a probability, and triangles represent outcomes.

FIGURE 13.

Decision tree for comparison of different methods of induction.

The model starts by dividing the population into those who deliver vaginally within the first 24 hours; have an emergency CS; and deliver vaginally after 24 hours.

Under each model of delivery, babies can either be born with no complications or be admitted to the NICU, which, in the context of randomised trials, we assumed relates to intervention and/or mode of delivery (CS or VD), but is less likely to relate to length of labour (i.e. whether a VD was within 24 hours of induction or not). NICU admission is divided into transitional care for those babies who need some medical treatment but are well enough to be cared for at the mother’s bedside, high-dependency care for babies who are recovering from critical illness and need a great deal of observation and support, and intensive care for babies who have serious potential health problems and need constant care to be kept alive. Utility scores and resource use were thought to vary depending on these levels of care.

Inputs to economic model

Effectiveness inputs

We required absolute probabilities for each of the paths in the branches of the tree shown in Figure 13, for each intervention. The NMA presented in Chapter 3 provided information on relative effects on these probabilities (in the form of ORs). In order to obtain absolute probabilities on all interventions we needed to apply these relative effects to absolute probabilities on a reference intervention. The choice of reference intervention is not important; however, it needs to be an intervention for which there is evidence available on absolute probabilities for all paths in our decision tree, and that evidence is relevant to the decision population under consideration. We chose vaginal PGE₂ (tablet) as the reference intervention, as there were several UK-based RCTs including this intervention for each of the probabilities that were required in the model.

The NMA presented in Chapter 3 analyses each of the outcomes independently. However, as can be seen from Figure 13, these outcomes are not independent. For example, a failure to achieve a VD in 24 hours includes both women who deliver by CS and those who deliver vaginally but not within 24 hours. A woman has to deliver in one of three ways: a VD within 24 hours (VD24), a CS or a VD after 24 hours (VD > 24). We therefore re-analysed the data, as described in Appendix 16, to estimate these three probabilities allowing for the dependence in the data. We assumed that the relative effects for NICU admission are independent of timing of delivery but dependent on mode of delivery. We also assumed that the probability of NICU admission is 1.5 times higher for a CS delivery (according to data on 2837 inductions of labour for live births in Liverpool Women’s NHS Foundation Trust in 2014). Under this assumption it can be verified that the probability of NICU admission for VD, p(NICUvd), and the probability of NICU admission for CS, p(NICUcs), can be obtained from the overall probability of NICU admission, p(NICU) using the following formulae: p(NICUvd) = p(NICU) × 2/(2 + p(CS)) and p(NICUcs) = p(NICU) × 3/(2 + p(CS)).

The proportion of CS births, p(CS), is based on the NMA presented in Chapter 3 being applied to the proportion estimated on the reference intervention, as described below and in Appendix 16. The relative effects for NICU admission from the NMA in Chapter 3 are applied to the probability of NICU admission on the reference intervention (Table 22) to obtain the absolute probability of NICU admission, p(NICU) for each intervention. The formulae above are then used to obtain p(NICUvd) and p(NICUcs).

TABLE 22 - Probabilities of events on reference treatment (PGE2 tablet)

Probability of	Posterior mean estimate (%)	95% CrI
VD within 24 hours	46	30 to 69
VD after 24 hours	30	15 to 49
CS	24	8 to 36
NICU admission	14	0 to 71

Note that all of these quantities are estimated using Bayesian Markov chain Monte Carlo (MCMC) simulation, which samples directly from the joint posterior distribution. The decision tree is evaluated for each of these simulated samples so that we have a simulation of utility and cost estimates for each intervention. These simulations ensure that the uncertainty in the model inputs are fully reflected in the estimation of costs and utilities.

There were five UK studies315,549,834,957 in our review that provided information on the probability of a CS on the reference intervention. There was one UK study in our review that provided information on the probability of VD within 24 hours, given no CS, on the reference intervention. There were two UK studies834 providing information on the probability of NICU admission on the reference intervention. These studies were chosen as they were the only UK-based studies that evaluated the reference treatment and were therefore thought to be most representative of the target population. Where there was more than one study, the reference intervention arms were pooled using single-arm meta-analysis (results shown in Table 22). A REs model was used for both the probability of CS and the probability of NICU admission as a result of the heterogeneity between the included studies. This is reflected in the wide CrIs for these probabilities (see Table 22).

We applied the ORs from the NMAs (see Chapter 3 and Appendix 16) to the absolute probabilities for the reference intervention (see Table 22), to obtain absolute probabilities for all interventions. Note that this was done within the Bayesian MCMC simulation, which samples from the joint posterior distribution so that all correlations and uncertainties are fully reflected in the estimates. The resulting estimates are given in Tables 23–26. Note that these results differ from those presented in Chapter 3. First, we are using a different reference intervention on which to apply relative effects. Second, because we are modelling the mode of delivery jointly (so probabilities sum to 1), the number of studies from which the VD within 24 hours is estimated is reduced (as we require studies to report all delivery outcomes fully). One point to note is that the estimate of the probability of a VD after 24 hours with i.v. oxytocin plus amniotomy is ‘0’, based on a single small study (25 women in this arm) with no women delivering vaginally after 24 hours.

TABLE 23 - Absolute probabilities of achieving VD within 24 hours

Posterior mean and 95% CrI are reported.

Treatment	Probability of achieving VD within 24 hours	95% CrI
i.v. oxytocin with amniotomy	0.78	0.6 to 0.91
Buccal/sublingual misoprostol	0.64	0.43 to 0.81
Vaginal misoprostol: dose ≥ 50 µg	0.62	0.43 to 0.77
Titrated (low-dose) oral misoprostol solution	0.55	0.31 to 0.74
Vaginal misoprostol: dose < 50 µg	0.52	0.33 to 0.71
Vaginal PGE2 gel	0.51	0.3 to 0.69
Oral misoprostol tablet: dose ≥ 50 µg	0.48	0.28 to 0.66
i.v. oxytocin	0.47	0.24 to 0.69
Vaginal PGE2 tablet	0.46	0.3 to 0.69
Sustained-release misoprostol insert	0.44	0.14 to 0.74
Double-balloon or Cook’s catheter	0.42	0.2 to 0.65
Vaginal PGE2 pessary (normal release)	0.42	0.19 to 0.66
Vaginal PGE2 pessary (slow release)	0.41	0.21 to 0.62
Foley catheter	0.41	0.19 to 0.63
Intracervical PGE2	0.40	0.2 to 0.59
Extra-amniotic PGE2	0.36	0.09 to 0.7
Oral misoprostol tablet: dose < 50 µg	0.33	0.1 to 0.61
NO	0.27	0.06 to 0.57
Mifepristone	0.16	0.16 to 0.16
Placebo	0.14	0.03 to 0.32

TABLE 24 - Absolute probabilities of achieving VD after 24 hours

Posterior mean and 95% CrI are reported.

Treatment	Probability of achieving VD after 24 hours	95% CrI
i.v. oxytocin with amniotomy	0	0 to 0
Buccal/sublingual misoprostol	0.19	0.06 to 0.39
Vaginal misoprostol: dose ≥ 50 µg	0.20	0.09 to 0.36
Titrated (low-dose) oral misoprostol solution	0.29	0.12 to 0.51
Vaginal PGE2 gel	0.30	0.15 to 0.49
Vaginal misoprostol: dose < 50 µg	0.30	0.14 to 0.49
Vaginal PGE2 tablet	0.30	0.15 to 0.49
i.v. oxytocin	0.31	0.12 to 0.54
Double-balloon or Cook’s catheter	0.33	0.13 to 0.56
Sustained-release misoprostol insert	0.33	0.07 to 0.65
Oral misoprostol tablet: dose ≥ 50 µg	0.34	0.16 to 0.53
Vaginal PGE2 pessary (slow release)	0.37	0.18 to 0.59
Vaginal PGE2 pessary (normal release)	0.38	0.15 to 0.63
Foley catheter	0.40	0.19 to 0.62
Intracervical PGE2	0.40	0.21 to 0.6
Extra-amniotic PGE2	0.41	0.1 to 0.73
Oral misoprostol tablet: dose < 50 µg	0.43	0.16 to 0.7
NO	0.53	0.21 to 0.77
Mifepristone	0.60	0.28 to 0.83
Placebo	0.63	0.41 to 0.8

TABLE 25 - Absolute probabilities of CS

Posterior mean and 95% CrI are reported.

Treatment	Probability of CS	95% CrI
Titrated (low-dose) oral misoprostol solution	0.16	0.06 to 0.31
Buccal/sublingual misoprostol	0.17	0.07 to 0.33
Vaginal misoprostol: dose < 50 µg	0.18	0.07 to 0.34
Mifepristone	0.18	0.06 to 0.36
Oral misoprostol tablet: dose ≥ 50 µg	0.18	0.07 to 0.34
Vaginal misoprostol: dose ≥ 50 µg	0.18	0.07 to 0.35
Foley catheter	0.19	0.07 to 0.36
Vaginal PGE2 gel	0.19	0.08 to 0.36
NO	0.20	0.08 to 0.37
Vaginal PGE2 pessary (normal release)	0.20	0.08 to 0.38
Intracervical PGE2	0.20	0.08 to 0.38
Vaginal PGE2 pessary (slow release)	0.21	0.08 to 0.39
i.v. oxytocin with amniotomy	0.21	0.08 to 0.41
i.v. oxytocin	0.22	0.09 to 0.41
Extra-amniotic PGE2	0.23	0.08 to 0.44
Sustained-release misoprostol insert	0.23	0.09 to 0.43
Placebo	0.23	0.09 to 0.42
Vaginal PGE2 tablet	0.24	0.08 to 0.3
Oral misoprostol tablet: dose < 50 µg	0.25	0.09 to 0.46
Double-balloon or Cook’s catheter	0.25	0.1 to 0.46

TABLE 26 - Absolute probabilities of NICU admission

Posterior mean and 95% CrI are reported.

Treatment	Probability of NICU admission	95% CrI
Extra-amniotic PGE2	0.09	0 to 0.57
Double-balloon or Cook’s catheter	0.11	0 to 0.66
Sustained-release misoprostol insert	0.11	0 to 0.66
Titrated (low-dose) oral misoprostol solution	0.12	0 to 0.69
Foley catheter	0.12	0 to 0.68
Vaginal PGE2 (tablet)	0.13	0 to 0.71
Vaginal PGE2 pessary (slow release)	0.13	0 to 0.7
Intracervical PGE2	0.13	0 to 0.71
Vaginal misoprostol: dose < 50 µg	0.13	0 to 0.7
Oral misoprostol tablet: dose < 50 µg	0.13	0 to 0.72
i.v. oxytocin	0.13	0 to 0.71
Buccal/sublingual misoprostol	0.13	0 to 0.7
Vaginal PGE2 (gel)	0.14	0 to 0.74
Vaginal PGE2 pessary (normal release)	0.14	0 to 0.74
Vaginal misoprostol: dose ≥ 50 µg	0.14	0 to 0.73
Oral misoprostol tablet: dose ≥ 50 µg	0.14	0 to 0.73
NO	0.14	0 to 0.73
i.v. oxytocin with amniotomy	0.19	0 to 0.84
Mifepristone	0.2	0 to 0.85
Placebo (no intervention)	0.16	0 to 0.77

Cost inputs

The perspective adopted for the economic evaluation was that of the service provider (UK NHS). In accordance with this perspective, the costs included in the economic analysis were the direct costs incurred as a result of the interventions. These included the intervention costs, costs of method of delivery and length of neonatal stay in level I, II or III units. The price year was 2012–13.

The costs of each method of delivery are given in Table 27, along with the minimum and maximum estimates. These were taken from the NHS reference costs 2012/13,958 which are the average unit cost to the NHS of providing secondary health care to NHS patients. These are calculated on a full absorption basis to identify the full cost of delivering the service. It was assumed that a VD within 24 hours would constitute a short stay under the costing code, whereas a VD after 24 hours would be coded as long stay and therefore incur higher costs. The cost of a long-stay emergency CS was also used as most emergency CSs result in a stay of > 24 hours. A uniform distribution for these costs was assumed in the model.

TABLE 27 - The NHS reference costs 2012–13958 for method of delivery and neonatal critical care admission

Outcome	Cost (£)	Lower (£)	Upper (£)	Currency code	Distribution
VD within 24 hours	1110	815	1345	NZ30C NEI-S	Uniform
VD after 24 hours	1919	1547	2344	NZ30C NEI-L	Uniform
Emergency CS	3727	2926	4289	NEI-L	Uniform
Neonatal critical care, transitional care (per day)	382	306	473	XA04Z	Uniform
Neonatal critical care, intensive care (per day)	1118	819	1301	XA01Z	Uniform
Neonatal critical care, high-dependency care (per day)	791	685	902	XA02Z	Uniform

Supporting documents for the NHS Reference Costs958 indicate that all activity relating to healthy babies is reported as part of the total costs of the maternity delivery episode, whereas babies who are unwell generate their own admission record. All hospitalised infants incur per-patient/day costs. The unit cost for an inpatient day is also given in Table 27.

Probability of admission to each level of neonatal care, and average length of stay in each level, was taken from data on term admissions at Liverpool Women’s NHS Foundation Trust. The data from 100 at-term NICU admissions between July and October 2014 showed that 19% of admissions were to intensive care, 7% were to high-dependency care and 74% were to transitional care. Median length of stay was 2 days for intensive care, 1.5 days for high-dependency care and 2 days for transitional care.

The other costs included in the analysis were the costs that were associated with the different methods of induction. These were taken from the British National Formulary (BNF)959 for the pharmacological interventions and from the published literature or manufacturer costs for the mechanical interventions.

Vaginal PGE₂ pessary (normal release) preparation varied considerably across trials and is not currently available on the NHS (see Chapter 3). In order to include this method, we assumed that the cost is equal to that for vaginal PGE₂ tablet and gel. Given these uncertainties, we have presented results excluding this intervention. The intervention costs are shown in Table 28.

TABLE 28 - Costs of methods of induction

Induction method	Cost (£)	Source
NO	0.16	BNF959
Vaginal misoprostol: dose ≥ 50 µg	0.67	BNF959
Vaginal misoprostol: dose < 50 µg	1.02	BNF959
Oral misoprostol tablet: dose ≥ 50 µg	1.02	BNF959
i.v. oxytocin	1.71	BNF959
Oral misoprostol tablet: dose < 50 µg	2.04	BNF959
Titrated (low-dose) oral misoprostol solution	2.04	BNF959
Buccal sublingual misoprostol	2.04	BNF959
i.v. oxytocin with amniotomy	2.67	BNF959
Mechanical methods: Foley catheter	4.00	Van Baaren 2013955
Mifepristone	17.50	BNF959
Vaginal PGE2 (tablet)	26.56	BNF959
Vaginal PGE2 (gel)	26.56	BNF959
Intracervical PGE2	26.56	BNF959
Vaginal PGE2 pessary (normal release)	26.56	Estimated
Vaginal PGE2 pessary (slow release)	30.00	BNF959
Sustained-release misoprostol insert	30.00	BNF959
Mechanical methods: double-balloon or Cook’s catheter	47.90	Manufacturer cost
Extra-amniotic PGE2	47.90	BNF959

Utility inputs

Ideally, we would capture health-related outcomes using QALYs measured using the European Quality of Life-5 Dimensions (EQ-5D™) instrument. However, our literature review did not identify any evidence on the EQ-5D for the outcomes in our model. Furthermore, because of the short time-horizon of our model, the EQ-5D is unlikely to be very sensitive to changes in outcomes in our model. Instead, we attributed a utility score to each of the outcomes in our model, which represents the strength of preferences for a set of health-related outcomes, where utility scores take values of between ‘0’ and ‘1’, with ‘1’ representing perfect health.

It was necessary to identify the best available utility estimates for health states that were associated with the consequences of induction of labour for use in the model. The health states used in the model included emergency CS and VD for the mother, and transitional care, high-dependency care and intensive care for the child.

A literature search was undertaken to identify evidence on these utility values within published literature. A search was carried out in PubMed, The Cochrane Library [including Cochrane Database of Systematic Reviews (CDSR), CENTRAL, Database of Abstracts of Reviews of Effects (DARE) and Economic Evaluations Databases], NHS EED and the Health Technology Assessment (HTA) database. Details of the search strategy are presented in Appendix 17. The number of studies retrieved in each search is shown in Table 29.

TABLE 29 - Number of studies retrieved in each search

Database	Number retrieved
HTA database	199
NHS EED	2247
The Cochrane Library	8908
PubMed	30,029

Studies were also identified through searching specialist health economics resources, such as the Cost-effectiveness Analysis Registry and reference list checking. After examining titles and abstracts to identify those that were likely to be relevant, 12 studies were found and full papers were obtained. The full-text papers were then screened by two reviewers (EK and NJW) to identify four relevant studies (Figure 14). The list of excluded full articles and reasons for their exclusion can be found in Appendix 17.

FIGURE 14.

Flow chart summarising the review process.

Many of the studies that were deemed inappropriate to inform the model relied on the use of assumptions or judgements obtained from expert panels to assign a utility value to the health states of emergency CS, VD and NICU admission, rather than using empirical evidence. Three of the studies960–962 identified that were deemed relevant elicited health-state valuations for these states using the standard gamble technique, which is a recognised preference-based measures of health-related quality of life. The other study963 elicited utilities using the prospective measure of preference method, which is a prospective modification of the time trade-off method and standard gamble tools that have been previously described and validated in other settings. 964

Table 30 lists the four studies,960–963 the utility values that the studies use and how they were derived. Three of the studies used appropriate respondents (patients) of a sufficient sample size to give robust estimates. The exception was the study by Plunkett and Grobman,962 which used a panel of five experts to assign utilities.

TABLE 30 - Included studies

VAS, visual analogue scale.

Study	Utility value given for:			How derived
	NICU	VD	Emergency CS
Turner et al.963 Vaginal delivery compared with elective CS: the views of pregnant women and clinicians. BJOG 2008;115:1494–502		Pain during labour: 0.92	0.59	Prospective Measure of Preference method Participant’s responses indicating the maximum level of risk (0–100%) that they would accept before opting for an elective CS were converted into utility scores, which ranged from 0 to 1 (n = 102 pregnant women)
Vandenbussche et al.960 Differences in the valuation of birth outcomes among pregnant women, mothers, and obstetricians. Birth 1999;26:178–83	Transient neurological symptoms: median 0.99; range 0.72–0.99			VAS and standard reference gamble given to 12 obstetricians, 15 pregnant women and 15 mothers (Used utilities elicited from mothers.)
Pham and Crowther961 Birth outcomes: utility values that postnatal women, midwives and medical staff express. BJOG 2003;110:121–7	Admission to neonatal nursery: median: 0.99, range: 0.70–0.99			VAS and standard gamble administered to 90 women in postnatal ward: 59 midwives and 31 medical staff (Used utilities elicited from postnatal women.)
Plunkett and Grobman962 Routine hepatitis C virus screening in pregnancy: a cost-effectiveness analysis. Am J Obstet Gynecol 2005;192:1153–61		Disutility of 0.0027, range 0.0037–0.0017	Disutility of 0.0046, range 0.0056–0.0036	Panel of five experts assigned utility values using time trade-off technique

None of the studies gives utility values for intensive, high dependency and transitional neonatal care, as required in our model. Vandenbussche et al. 960 gives utilities for ‘transient neurological symptoms’, and Pham and Crowther961 give utilities for admission to ‘neonatal nursery’. It was not clear in either of these studies if the utilities relate to the mother, baby, or both. In the absence of utilities specifically for the health states in our model, we used the lower interval reported in these two studies (0.7 from Table 30) to represent intensive care, the higher interval (0.99 from Table 30) to represent transitional care and the midpoint (0.845) to represent high-dependency care. There is clearly a high degree of uncertainty in these values, and so we conducted a sensitivity analysis as detailed in Table 31.

TABLE 31 - Sets of utility estimates varied in sensitivity analysis

Model run	Intensive care	High-dependency care	Transitional care
Base case	0.7	0.845	0.99
Sensitivity analysis 1	0.7	0.7	0.99
Sensitivity analysis 2	0.7	0.7725	0.99
Sensitivity analysis 3	0.57	0.78	0.99
Sensitivity analysis 4	0.57	0.675	0.99

In sensitivity analyses 1 and 2 we vary the utility for high-dependency care to 0.7 (equal to intensive care), and 0.7725 [midpoint between 0.7 and 0.845 (base case)]. In sensitivity analyses 3 and 4 we assume a lower utility score for intensive care (0.57 based on our own small survey described below). In sensitivity analysis 3 we use the midpoint between 0.57 and 0.99 (0.78) for high-dependency care, and in sensitivity analysis 4 we use a quarter of the way between the 0.57 and 0.99 (0.675) for high-dependency care.

Both the Turner et al. study963 and the Plunkett and Grobman study962 provide estimates of utilities relating to mode of delivery; however, we use only the values from Turner et al. ,963 as it is based on 102 pregnant women, rather than five experts. We therefore used the utility values of 0.92 and 0.59 for VD and emergency CS, respectively, as reported in Turner et al. 963 (see Table 30). However, no confidence intervals are reported for these figures, so we cannot reflect the uncertainty in the estimates.

Because of the limited evidence in the literature on utilities, we conducted our own small survey to help us reflect uncertainty in the utilities and obtain limits for sensitivity analysis. We administered a questionnaire asking respondents to rate different health states. The full questionnaire and results are given in Appendix 18. An example question is given in Figure 15.

FIGURE 15.

Example question from questionnaire on different health states.

This type of rating scale is called a visual analogue scale (VAS) and is commonly used as a method of measuring preferences for health outcomes. 965

Ten respondents completed this questionnaire. This group included all members of the project steering group including clinicians, health economists, systematic reviewers and a patient representative. The health states evaluated were the health of the mother following normal VD and CS, and the health of the mother and child following the child’s admission to the ICU, high dependency unit or transitional care unit. The data were analysed using a model that accounted for the between-respondent variability in overall level of the utility scores, and assumed common mean differences in utility scores for the different outcomes. Details of the statistical model are given in Appendix 18.

The estimated scores from this questionnaire were 0.65 (CrI 0.51 to 0.79) for a VD and 0.42 (CrI 0.17 to 0.67) for CS. Interestingly, although the absolute values of the scores differ, the ratio of the utilities for VD and CS taken from Turner et al. 963 agrees almost exactly with those arising from our own questionnaire. We therefore felt it appropriate to calibrate the scores from our questionnaire to those obtained in Turner et al. 963 to obtain uncertainty limits to put around the estimates from Turner et al. 963 for use in the economic model.

Our questionnaire obtained scores for intensive care, high-dependency care and transitional care from both the mother’s and baby’s perspective. Summing these scores for mother and baby for transitional care gave a value of ‘1’, very similar to the 0.99 obtained from the literature review. On this basis, summing the values for mother and baby from our questionnaire for intensive care gives a value of 0.57, which we use as a lower limit in our sensitivity analysis (detailed in Table 31).

The final utility values that went into the model are shown in Table 32.

TABLE 32 - Utility estimates used in model

The first column shows the utilities used for mode of delivery; the second column shows the utilities used for NICU admission type of care; and the third column is the product of the first two columns, corresponding to branches of the decision tree (see Figure 13).

Delivery mode: utility (95% CrI)	NICU admission (base-case utility, see Table 27)	Delivery mode and NICU admission: product of utilities (95% CrI)
VD 0.92 (0.72 to 1)	None (1)	0.92 (0.72 to 1)
	Transitional care (0.99)	0.91 (0.71 to 0.99)
	High-dependency care (0.845)	0.78 (0.61 to 0.85)
	Intensive care (0.7)	0.64 (0.50 to 0.7)
Emergency CS 0.59 (0.25 to 0.95)	None (1)	0.59 (0.25 to 0.95)
	Transitional care (0.99)	0.58 (0.25 to 0.94)
	High-dependency care (0.845)	0.50 (0.21 to 0.80)
	Intensive care (0.7)	0.41 (0.18 to 0.67)

Results

Base-case results

Table 33 shows the expected total cost and expected total utility for each treatment, averaged over the simulation sample along with their CrIs. Interventions are ordered by increasing expected total cost (treatment costs plus resource costs), with buccal/sublingual misoprostol and i.v. oxytocin with amniotomy having the lowest expected total cost, and placebo (no intervention) having the highest expected total cost. Note that all methods of induction have lower expected total costs than placebo (no intervention) because they reduce costly outcomes (VD in > 24 hours, CS and NICU admission). Titrated (low-dose) oral misoprostol solution has the highest expected utility, very closely followed by buccal/sublingual misoprostol, mifepristone, i.v. oxytocin with amniotomy and vaginal misoprostol (dose ≥ 50 µg). Intracervical PGE₂ has the lowest expected utility. As the majority of interventions (all except intracervical PGE₂) have no more than a 0.02 difference in expected utility between them, they could be assumed to be clinically equivalent, so that a decision between them is effectively based on minimising total costs. Note that the confidence intervals show that there is a high degree of uncertainty in these estimates.

TABLE 33 - Base case: expected total costs, expected total utilities, ICERs and expected net benefit at a £20,000 willingness-to-pay threshold

CI, confidence interval.

Note

£21,190 is the additional expected cost per additional unit gain in utility required for titrated (low-dose) oral misoprostol solution compared with buccal/sublingual misoprostol.

Treatment	Expected total cost, £ (95% CI)	Expected total utility (95% CI)	Expected net benefit (£)	ICER (£)
Buccal/sublingual misoprostol	1747.18 (1341.57 to 1472.34)	0.821 (0.68 to 0.95)	14,668.72
i.v. oxytocin with amniotomy	1747.80 (1275.41 to 2370.82)	0.82 (0.67 to 0.95)	14,652.13	Dominated
Vaginal misoprostol: dose ≥ 50 µg	1789.56 (1386.41 to 2270.74)	0.82 (0.68 to 0.95)	14,603.51	Dominated
Titrated (low-dose) oral misoprostol solution	1799.55 (1403.44 to 2262.1)	0.823 (0.68 to 0.96)	14,658.28	21,190
Vaginal misoprostol: dose < 50 µg	1852.56 (1456.01 to 2325.54)	0.819 (0.68 to 0.95)	14,533.98	Dominated
Oral misoprostol tablet: dose ≥ 50 µg	1906.19 (1499.21 to 2384.89)	0.819 (0.68 to 0.95)	14,467.15	Dominated
Vaginal PGE2 gel	1935.79 (1517.97 to 2429.53)	0.817 (0.67 to 0.95)	14,402.37	Dominated
Foley catheter	1968.64 (1550.28 to 2463.38)	0.815 (0.67 to 0.95)	14,328.52	Dominated
i.v. oxytocin	1977.39 (1536.48 to 2518.6)	0.809 (0.66 to 0.95)	14,195.63	Dominated
Sustained-release misoprostol insert	1997.08 (1480.46 to 2597.86)	0.805 (0.65 to 0.95)	14,108.39	Dominated
Vaginal PGE2 pessary (normal release)	2015.76 (1569.43 to 2533.94)	0.811 (0.66 to 0.95)	14,210.27	Dominated
Intracervical PGE2	2033.03 (1614.6 to 2532.76)	0.633 (0.53 to 0.74)	10,617.17	Dominated
Vaginal PGE2 pessary (slow release)	2036.15 (1602.91 to 2551.89)	0.81 (0.66 to 0.95)	14,162.42	Dominated
Vaginal PGE2 tablet	2042.64 (1638.01 to 2565.19)	0.805 (0.65 to 0.95)	14,054.25	Dominated
Extra-amniotic PGE2	2093.96 (1567.05 to 2684.18)	0.804 (0.65 to 0.95)	13,982.18	Dominated
Double-balloon or Cook’s catheter	2097.74 (1618.43 to 2682.1)	0.8 (0.64 to 0.95)	13,906.29	Dominated
Oral misoprostol tablet: dose < 50 µg	2140.28 (1644.79 to 2738.28)	0.802 (0.64 to 0.94)	13,898.03	Dominated
NO	2141.74 (1662.1 to 2676.64)	0.816 (0.67 to 0.94)	14,179.69	Dominated
Mifepristone	2202.28 (1709.58 to 2742.8)	0.821 (0.69 to 0.95)	14,210.41	Dominated
Placebo (‘no intervention’)	2304.82 (1847.79 to 2822.48)	0.805 (0.65 to 0.94)	13,788.52	Dominated

Any intervention that has a higher expected cost and lower expected utility than another intervention is said to be dominated by that intervention. As can be seen from Table 33, all treatments apart from titrated low-dose oral misoprostol solution are dominated by buccal/sublingual misoprostol, which is more effective, in terms of increased utility, and less expensive than the other interventions.

As titrated (low-dose) oral misoprostol solution is non-dominated relative to buccal/sublingual misoprostol, an ICER is computed:

⁽³⁾ I C E R = additional expected cost additional expected utility = £ 4 2 . 3 8 0 . 0 0 2 = £ 2 1 , 1 9 0 .

Therefore, £21,190 is the additional expected cost per additional unit gain in utility required for titrated (low-dose) oral misoprostol solution compared with buccal/sublingual misoprostol.

The expected total costs and expected utilities are displayed graphically in a cost-efficiency frontier (Figure 16). Any intervention above the line is not cost-effective compared with interventions lower down for a given expected utility. The graph shows that all of the other interventions apart from buccal/sublingual misoprostol and titrated (low-dose) oral misoprostol are above the line and are therefore dominated, as they are more expensive and less effective. i.v. oxytocin lies very close to the line. Intracervical PGE₂ is removed from the graph for visualisation purposes, as it is considerably less effective than the rest of the treatments and also relatively expensive, placing it far from the line. Placebo is the treatment that has the highest expected total cost and is therefore far from the line.

FIGURE 16.

Base case: cost-effectiveness efficiency frontier.

The expected net benefit at a £20,000 willingness-to-pay threshold (see Table 33) is highest for buccal/sublingual misoprostol (£14,669), closely followed by titrated (low-dose) oral misoprostol solution (£14,658) and i.v. oxytocin with amniotomy (£14,652) and lowest for intracervical PGE₂ (£10,617).

We present the uncertainty surrounding the cost-effectiveness of the various interventions, using a CEAC (Figure 17) and the cost-effectiveness plane (Figure 18).

FIGURE 17.

Base-case CEAC. Plotted against different willingness-to-pay per unit increase in utility (ceiling ratio). Note the curves are unchanged for ceiling ratios of > £50,000. Note: The non-labelled interventions have not been specified because of their close proximity to each other.

FIGURE 18.

Base case: incremental cost-effectiveness plane.

The CEACs (see Figure 17) plot the probability that each of the interventions is the most cost-effective by computing the proportion of simulations for which that intervention had the highest net benefit for a given willingness-to-pay per unit increase in utility. Out of the 19 interventions evaluated, only three had a probability of > 10% of being cost-effective at any willingness-to-pay value: titrated (low-dose) oral misoprostol solution, buccal/sublingual misoprostol and i.v. oxytocin with amniotomy. However, the results for i.v. oxytocin with amniotomy were very uncertain, and i.v. oxytocin also had a high probability of being the least cost-effective. To avoid misleading conclusions, we have removed i.v. oxytocin with amniotomy from Figure 17, and, for clarity, give labels only for interventions for which it was clear that the probability of being cost-effective is > 10%. Figure 17 shows that at any willingness-to-pay value up until around £23,000, buccal/sublingual misoprostol has the highest probability of being cost-effective. Above this threshold, titrated low-dose oral misoprostol solution has the highest probability of being cost-effective. This probability is never > 35%, indicating a large degree of uncertainty in the optimal intervention.

The high degree of uncertainty between these interventions is seen clearly in the cost-effectiveness plane (see Figure 18), which plots the simulated pairs of incremental utility and incremental cost values for each intervention (compared with vaginal PGE₂ tablet). As there are a large number of interventions to display, and the majority of interventions were very similar in terms of costs and utilities, the plot is unreadable if all interventions are included. For visual clarity, we plot only the interventions that were found to have had a > 10% probability of being cost-effective of at any willingness-to-pay value, along with intracervical PGE₂, the intervention with the lowest average utility.

As can be seen from the graph, the majority of the points for buccal/sublingual misoprostol, titrated (low-dose) oral misoprostol solution and i.v. oxytocin with amniotomy are plotted in the bottom right-hand corner, indicating that these interventions are more effective and less expensive than vaginal PGE₂ tablet. However, the location of some of the points in the other quadrants indicates that this is not certain. All of the points for intracervical PGE₂, for example, are plotted in the top- and bottom-left quadrants, showing that although there is uncertainty in the cost, intracervical PGE₂ never has a utility score higher than vaginal PGE₂ tablet.

Sensitivity analysis to assumed utilities

Varying the utility estimates, as detailed in Table 31, had a very minor effect on the results. The interventions were ranked from lowest to highest expected cost in the same order and the expected utilities varied only on the second or third decimal point.

Subgroup analysis (i): women with intact membranes only

To examine the effect that membrane status had on the results, a scenario analysis was carried out restricting to mothers with intact membranes only. When we included all interventions for which we had sufficient information to evaluate the model, only 13 out of a total of 34 interventions (see Table 34 and see Appendix 16) were included in analysis, and the remaining interventions were excluded. Note that placebo (no intervention) was not included in this analysis, so comparisons with no intervention cannot be made.

Table 34 shows the expected total utility and expected total cost for each treatment when the analysis is limited to women with intact membranes. Interventions are again ordered in order of increasing expected cost (treatment costs plus resource costs) with titrated (low-dose) oral misoprostol solution now having the highest expected total cost and vaginal misoprostol (dose < 50 µg) and i.v. oxytocin with amniotomy having the lowest expected cost. Titrated (low-dose) oral misoprostol solution still has the highest expected utility, and intracervical PGE₂ still has the lowest expected utility. The confidence intervals again show that there is a high degree of uncertainty in these estimates.

TABLE 34 - Subgroup analysis: women with intact membranes only, excluding vaginal PGE2 pessary (normal release)a

CI, confidence interval.

Expected total costs, expected total utilities, ICER and expected net benefit at a £20,000 willingness-to-pay value.

Note

£156.66 is the additional expected cost per additional unit gain in utility required for i.v. oxytocin with amniotomy compared with vaginal misoprostol in women with intact membranes only.

£39,501 is the additional expected cost per additional unit gain in utility required for titrated (low-dose) oral misoprostol solution compared with i.v. oxytocin with amniotomy in women with intact membranes only.

Treatment	Expected total cost, £ (95% CI)	Expected total utility (95% CI)	Expected net benefit (£)	ICER (£)
Vaginal misoprostol: dose < 50 µg	1928.96 (1571.86 to 2338.89)	0.82 (0.69 to 0.94)	14,464.22
i.v. oxytocin with amniotomy	1929.9 (1487.64 to 2439.18)	0.826 (0.7 to 0.94)	14,586.48	156.66
Buccal/sublingual misoprostol	1936.01 (1516.6 to 1816.31)	0.817 (0.68 to 0.94)	14,400.68	Dominated
Vaginal misoprostol: dose ≥ 50 µg	2000.32 (1634.83 to 2416.3)	0.815 (0.69 to 0.94)	14,287.56	Dominated
Vaginal PGE2 pessary (normal release)	2018.92 (1612.79 to 2494.27)	0.814 (0.68 to 0.94)	14,252.13	Dominated
Oral misoprostol tablet: dose ≥ 50 µg	2028.67 (1662.47 to 2439.99)	0.82 (0.7 to 0.94)	14,362.26	Dominated
Foley catheter	2065.24 (1691.42 to 2497.22)	0.813 (0.68 to 0.94)	14,185.49	Dominated
Vaginal PGE2 gel	2165.47 (1777.15 to 2608.8)	0.813 (0.68 to 0.94)	14,096.27	Dominated
Vaginal PGE2 tablet	2193.74 (1809.57 to 2617.3)	0.803 (0.67 to 0.93)	13,861.77	Dominated
Intracervical PGE2	2195.47 (1809.48 to 2640.88)	0.638 (0.54 to 0.74)	10,563.31	Dominated
Vaginal PGE2 pessary (slow release)	2219.12 (1851.24 to 2668.99)	0.807 (0.68 to 0.93)	13,924.89	Dominated
Double-balloon or Cook’s catheter	2249.43 (1824.03 to 2759.69)	0.793 (0.65 to 0.93)	13,607.27	Dominated
Titrated (low-dose) oral misoprostol solution	2403.92 (1841.58 to 3084.74)	0.832 (0.71 to 0.93)	14,224.30	39,501.66

As can be seen from Table 34, all interventions apart from titrated (low-dose) oral misoprostol solution and i.v. oxytocin with amniotomy are dominated by vaginal misoprostol (dose < 50 µg), which is more effective in terms of increased utility, and less expensive.

As i.v. oxytocin with amniotomy is non-dominated relative to vaginal misoprostol (dose < 50 µg), an ICER is computed:

⁽⁴⁾ I C E R = additional expected cost additional expected utility = £ 0 . 9 4 0 . 0 0 6 = £ 1 5 6 . 6 6 .

Therefore, £156.66 is the additional expected cost per additional unit gain in utility required for i.v. oxytocin with amniotomy compared with vaginal misoprostol in women with intact membranes only.

As titrated (low-dose) oral misoprostol solution is non-dominated relative to i.v. oxytocin with amniotomy, an ICER is also computed:

⁽⁵⁾ I C E R = additional expected cost additional expected utility = £ 4 7 4 . 0 2 0 . 0 1 2 = £ 3 9 , 5 0 1 . 6 6 .

Therefore, £39,501.66 is the additional expected cost per additional unit gain in utility required for titrated (low-dose) oral misoprostol solution compared with i.v. oxytocin with amniotomy in women with intact membranes only.

The intervention with the highest expected net benefit at £20,000 threshold is i.v. oxytocin with amniotomy (£14,586), followed by vaginal misoprostol (dose < 50 µg) (£14,464), and the intervention with the lowest expected net benefit is intracervical PGE₂ at £10,563.

The CEAC for women with intact membranes only is presented in Figure 19. i.v. oxytocin with amniotomy, titrated (low-dose) oral misoprostol solution, buccal/sublingual misoprostol and vaginal misoprostol (dose < 50 µg) were the only four treatments with a probability of being cost-effective of > 10% of any willingness-to-pay value (ceiling ratio). i.v. oxytocin with amniotomy has the highest probability of being cost-effective at any value of the ceiling ratio with a probability of around 45%.

FIGURE 19.

Cost-effectiveness acceptability curve for subgroup analysis (i): women with intact membranes only. Note: The non-labelled interventions have not been specified because of their close proximity to each other.

The incremental cost-effectiveness plane for the four interventions with probability of being cost-effective of > 10% is presented in Figure 20, showing the high degree of uncertainty in the costs and effects of these interventions.

FIGURE 20.

Incremental cost-effectiveness plane for subgroup analysis (i): women with intact membranes only.

Subgroup analysis (ii): women with an unfavourable cervix only

To examine the effect that Bishop score had on the results, a scenario analysis was carried out restricting to mothers with an unfavourable cervix (Bishop score < 6). When we included all of the interventions for which we had sufficient information to evaluate the model, 19 interventions out of a total of 34 interventions (see Table 35 and Appendix 16) were included in the analysis, and the remaining were excluded.

Table 35 shows the expected total utility and expected total cost for each intervention when the analysis is limited to women with an unfavourable cervix. Interventions are again ordered by increasing expected total cost with buccal/sublingual misoprostol having the lowest expected total cost and placebo having the highest expected total cost, as in the base case. Titrated (low-dose) oral misoprostol solution and buccal/sublingual misoprostol have the highest expected utility, and intracervical PGE₂ still has the lowest expected utility. The confidence intervals again show that there is a high degree of uncertainty in these estimates.

TABLE 35 - Subgroup analysis: women with an unfavourable cervix onlya

CI, confidence interval.

Expected total costs, expected total utilities, and expected net benefit at a £20,000 willingness-to-pay value.

Treatment	Expected total cost, £ (95% CI)	Expected total utility (95% CI)	ICER	Expected net benefit (£)
Buccal/sublingual misoprostol	1803.03 (1209.38 to 2293.03)	0.805 (0.62 to 0.96)		14,296.29
Titrated (low-dose) oral misoprostol solution	1833.93 (1228.19 to 2681.17)	0.805 (0.62 to 0.95)	Dominated	14,268.94
Vaginal misoprostol: dose ≥ 50 µg	1860.48 (1237.3 to 2736.31)	0.799 (0.61 to 0.95)	Dominated	14,125.24
Vaginal misoprostol: dose < 50 µg	1900.34 (1269.91 to 2767.69)	0.8 (0.61 to 0.95)	Dominated	14,096.55
Oral misoprostol tablet: dose ≥ 50 µg	1922.13 (1281.71 to 2778.67)	0.8 (0.61 to 0.95)	Dominated	14,083.50
Vaginal PGE2 gel	1966.08 (1316.53 to 2849.77)	0.796 (0.6 to 0.95)	Dominated	13,958.18
Foley catheter	1984.89 (1332.08 to 2845.84)	0.796 (0.6 to 0.95)	Dominated	13,937.91
Intracervical PGE2	2033.89 (1370.72 to 2917.34)	0.642 (0.5 to 0.8)	Dominated	10,797.93
Vaginal PGE2 pessary (normal release)	2047.53 (1367.65 to 2942.25)	0.79 (0.58 to 0.95)	Dominated	13,750.04
Sustained-release misoprostol insert	2082.66 (1352.56 to 3024.87)	0.784 (0.57 to 0.95)	Dominated	13,594.43
Vaginal PGE2 pessary (slow release)	2102.42 (1412.2 to 2993.83)	0.788 (0.58 to 0.95)	Dominated	13,666.30
Vaginal PGE2 tablet	2106.02 (1418.6 to 3012.11)	0.783 (0.57 to 0.94)	Dominated	13,562.65
NO	2115.85 (1424.43 to 2958.84)	0.795 (0.59 to 0.94)	Dominated	13,792.94
i.v. oxytocin	2137.78 (1433.27 to 3017.3)	0.787 (0.58 to 0.95)	Dominated	13,604.63
Double-balloon or Cook’s catheter	2159.86 (1422.1 to 3114.44)	0.778 (0.55 to 0.94)	Dominated	13,397.99
Oral misoprostol tablet: dose < 50 µg	2166.04 (1420.9 to 3096.83)	0.78 (0.56 to 0.95)	Dominated	13,434.70
Mifepristone	2182.01 (1516.15 to 2987.41)	0.801 (0.61 to 0.95)	Dominated	13,831.39
Placebo	2276.45 (1599 to 3112.04)	0.784 (0.57 to 0.94)	Dominated	13,407.56

As can be seen from Table 35, all other interventions are dominated by buccal/sublingual misoprostol, which is more effective in terms of increased utility (or equivalent in the case of titrated (low-dose) oral misoprostol) and less expensive than all other treatments. However, as in the other analyses, there is little difference between the utility scores.

The intervention with the highest expected net benefit is buccal/sublingual misoprostol (£14,296) followed by titrated (low-dose) oral misoprostol solution (£14,269) then vaginal misoprostol (dose ≥ 50 µg) (£14,125), and the intervention with the lowest expected net benefit is intracervical PGE₂ at £10,798.

The CEAC for women with an unfavourable cervix subgroup is presented in Figure 21. Buccal/sublingual misoprostol has the highest probability of being most cost-effective, followed by titrated (low-dose) oral misoprostol solution, but there is a high degree of uncertainty in these results, with the probability being around 50%.

FIGURE 21.

Cost-effectiveness acceptability curve for subgroup analysis (ii): women with an unfavourable cervix only. Note: The non-labelled interventions have not been specified because of their close proximity to each other.

The incremental cost-effectiveness plane for the subgroup analysis (Figure 22) shows incremental costs and utilities (compared with vaginal PGE₂ tablet) for the two interventions that had a probability of being cost-effective of > 10%. The majority of the points are located in the bottom right-hand quadrant, indicating that they are likely to be less expensive and more effective than vaginal PGE₂ tablet.

FIGURE 22.

Incremental cost-effectiveness plane for subgroup analysis (ii): women with an unfavourable cervix only.

Chapter 5 Discussion

Acknowledgements

Steering group members: Declan Devane, Polly Griffiths, Paul Jacklin, Tony Kelly.

Thanks to members of the steering group for providing valuable advice at various stages of the project and for completing the utilities questionnaires. We would also like to thanks staff in the CPCG: Frances Kellie managed project finances, Lynn Hampson and Sarah Perry carried out the search and retrieved copies of reports, and Jill Fitzpatrick, Helen West and Kate Navratavan contributed to data extraction. Finally, we would like to thank Professor Stavros Petrou, University of Warwick, for advice regarding the utilities, and Liverpool Women’s NHS Trust for providing data to inform the economic model cost-effectiveness analysis.

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