The Cochrane Database of Systematic Reviews 2006 Issue 3
Copyright 2006 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

Plain language summary
There is not enough evidence about the effects of amniotomy alone (deliberate rupture of the membranes) to induce labour.
Sometimes it is advisable to get labour started (induction) because of concerns about either the pregnant woman or her unborn baby. Amniotomy has been used as either the only method of inducing labour if the membranes can be reached, or used with drugs such as oxytocin or prostaglandin. Amniotomy may be preferred by women wanting a drug-free labour and it is cheap. However, it can be uncomfortable, and if after amniotomy there is a long time interval before the baby is born there is a risk of infection. There is also the risk of the cord coming out before the baby. This review of trials found that there is not enough evidence about the effects of amniotomy alone for the induction of labour.

Amniotomy (deliberate rupture of the membranes) is a simple procedure which can be used alone for induction of labour if the membranes are accessible, thus avoiding the need for pharmacological intervention. However, the time interval from amniotomy to established labour may not be acceptable to clinicians and women, and in a number of cases labour may not ensue. This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology.

To determine the effects of amniotomy alone for third trimester labour induction in women with a live fetus.

Search strategy
The Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Controlled trials register and bibliographies of relevant papers.

Selection criteria
The criteria for inclusion included the following: (1) clinical trials comparing amniotomy alone 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 or pseudo-random allocation to the treatment or control group; (3) ideally 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
This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology. A strategy was 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 the series of primary reviews arranged by methods of induction of labour. The data from the primary reviews will be incorporated into a series of secondary reviews, arranged by category of woman to reflect clinical scenarios. To avoid duplication of data in the primary reviews, the labour induction methods have been listed in a specific order, from one to 25. Each primary review includes comparisons between one of the methods (from two to 25) with only those methods above it on the list. This review includes comparisons between amniotomy alone (number 5 on the list) with only those methods above it on the list (no treatment / placebo; intravaginal prostaglandins; intracervical prostaglandins; and oxytocin alone).

Main results
Two trials comprising 50 and 260 women respectively were eligible for inclusion in this review. No conclusions could be drawn from comparisons of amniotomy alone versus no intervention, and amniotomy alone versus oxytocin alone (small trial, only one pre-specified outcome reported). No trials compared amniotomy alone with intracervical prostaglandins. One trial compared amniotomy alone with a single dose of vaginal prostaglandins for women with a favourable cervix, and found a significant increase in the need for oxytocin augmentation in the amniotomy alone group (44% versus 15%; RR 2.85, 95% CI 1.82-4.46). This should be viewed with caution as this was the result of a single centre trial. Furthermore, secondary intervention occurred 4 hours after amniotomy, and this time interval may not have been appropriate.

Authors' conclusions
Data are lacking about the value of amniotomy alone for induction of labour. While there are now other modern methods available for induction of labour (pharmacological agents), there remain clinical scenarios where amniotomy alone may be desirable and appropriate, and this method is worthy of further research. This research should include evaluation of the appropriate time interval from amniotomy to secondary intervention, women and caregivers' satisfaction and economic analysis.