Background: Prostaglandins have been used for induction of labour since the 1960s. Initial work focused on prostaglandin F2a as prostaglandin E2 was considered unsuitable for a number of reasons. With the development of alternative routes of administration, comparisons were made between various formulations of vaginal prostaglandins. This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology.
Objectives: To determine the effects of vaginal prostaglandins E2 and F2a for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment or other vaginal prostaglandins (except Misoprostol).
Search strategy: The Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Controlled trials register and bibliographies of relevant papers. Last searched: November 2000.
Selection criteria: The criteria for inclusion included the following: (1) clinical trials comparing vaginal prostaglandins used for third trimester cervical ripening or labour induction with placebo/no treatment or other methods listed above it on a predefined list of labour induction methods; (2) random allocation to the treatment or control group; (3) adequate allocation concealment; (4) violations of allocated management not sufficient to materially affect conclusions; (5) clinically meaningful outcome measures reported; (6) data available for analysis according to the random allocation; (7) missing data insufficient to materially affect the conclusions.
Data collection and analysis: A strategy has been developed to deal with the large volume and complexity of trial data relating to labour induction. This involved a two-stage method of data extraction. The initial data extraction was done centrally, and incorporated into a series of primary reviews arranged by methods of induction of labour, following a standardised methodology. The data was then extracted from the primary reviews into a series of secondary reviews, arranged by category of woman. To avoid duplication of data in the primary reviews, the labour induction methods were listed in a specific order, from one to 23. Each primary review included comparisons between one of the methods (from two to 23) with only those methods above it on the list.
Main results: In total, 94 studies were considered; 42 have been excluded and 52 included examining a total of 9402 women. Vaginal prostaglandin E2 compared with placebo or no treatment reduced the likelihood of vaginal delivery not being achieved within 24 hours (18% vs. 99%, RR 0.19, 95% CI 0.14,0.25), the caesarean section rates were not different between groups although the risk of uterine hyperstimulation with fetal heart rate changes was increased (4.6% vs. 0.51%, RR 4.14, 95% CI 1.93, 8.90). Comparison of vaginal prostaglandin F2a with placebo showed no increase in caesarean section rates but the cervical score was more likely to be improved (15% vs. 60%, RR 0.25, 95% CI 0.13,0.49), and the risk of oxytocin augmentation reduced (53.9% vs. 89.1%, RR 0.60, 95% CI 0.43,0.84) with the use of vaginal PGF2a. There were insufficient data to make meaningful conclusions for the comparison of vaginal PGE2 and PGF2a. PGE2 tablet, gel and pessary appear to be as efficacious as each other. Lower dose regimes, as defined in the review, appear as efficacious as higher dose regimes.
Reviewer's conclusions: The primary aim of this review was to examine the efficacy of vaginal prostaglandin E2 and F2a. This is reflected by an increase in successful vaginal delivery rates in 24 hours, no increase in operative delivery rates and significant improvements in cervical favourability within 24-48 hours. Further research is needed to quantify the cost-analysis of induction of labour with vaginal prostaglandins, with special attention to different methods of administration.