• J Thomas, A J Kelly, and J Kavanagh.
• Clinical Effectiveness Support Unit, Royal College of Obstetricians and Gynaecologists, 27 Sussex Place, Regent's Park, London, UK, NW1 4RG. jthomas@rcog.org.uk
• Cochrane Db Syst Rev. 2001 Jan 1; 2001 (4): CD003393CD003393.

BackgroundStudies in sheep showed that there is a pre-labour rise in oestrogen and a decrease in progesterone, both of these changes stimulate prostaglandin production and may help initiate labour. Though oestrogen has been suggested as an effective cervical ripening or induction agent, research in humans have failed to demonstrate a similar physiological mechanism. The use of oestrogen as an induction agent is not currently common practice, as such this systematic review should be regarded as an historical review. This is one of a series of reviews of methods of cervical ripening and labour induction using a standardised methodology.ObjectivesTo determine, from the best available evidence, the effectiveness and safety of oestrogens alone or with amniotomy for third trimester cervical ripening and induction of labour in comparison with other methods of induction of labour.Search StrategyThe Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Controlled Trials Register and bibliographies of relevant papers. Last searched: April 2001.Selection Criteria(1) randomised controlled trials comparing oestrogens alone 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 AnalysisA generic 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.Main ResultsWhen comparing oestrogen with placebo there was no difference between the rate of caesarean section (7.1% versus 10.3%, relative risk (RR) 0.70, 95% confidence interval (CI) 0.30,1.62). There were no differences between rates of uterine hyperstimulation with or without fetal heart rate changes or instrumental vaginal delivery. None of the studies reported the rates of either vaginal delivery not achieved in 24 hours, or cervix unfavourable/unchanged after 12-24 hours. There were insufficient data to make any meaningful conclusions when comparing oestrogen with vaginal PGE2, intracervical PGE2, oxytocin alone or extra amniotic PGF2a, as to whether oestrogen is effective in inducing labour.Reviewer's ConclusionsThere were insufficient data to draw any conclusions regarding the efficacy of oestrogen as an induction agent.

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