Background: Early amniotomy has been advocated as a component of the active management of labour. Several randomised trials comparing routine amniotomy to an attempt to conserve the membranes have been published. Their limited sample sizes limit their ability to address the effects of amniotomy on indicators of maternal and neonatal morbidity.
Objectives: To study the effects of amniotomy on the rate of Cesarean delivery and on other indicators of maternal and neonatal morbidity (Apgar less than 7 at 5 minutes, admission to NICU).
Search strategy: The register of clinical trials maintained and updated by the Cochrane Pregnancy and Childbirth Group.
Selection criteria: All acceptably controlled trials of amniotomy during first stage of labour were eligible.
Data collection and analysis: Data were extracted by two trained reviewers from published reports. Trials were assigned methodological quality scores based on a standardized rating system. Typical odds ratios (ORs) were calculated using Peto's method.
Main results: Amniotomy was associated with a reduction in labour duration of between 60 and 120 minutes. There was a marked trend toward an increase in the risk of Cesarean delivery: OR = 1.26; 95% Confidence Interval (CI)=0.96-1.66. The likelihood of a 5 minute Apgar score less than 7 was reduced in association with early amniotomy (OR = 0.54; 95% CI = 0.30-0.96). Groups were similar with respect to other indicators of neonatal status (arterial cord pH, NICU admissions). There was a statistically significant association of amniotomy with a decrease in the use of oxytocin: OR = 0.79; 95% CI = 0.67-0.92.
Authors' conclusions: Routine early amniotomy is associated with both benefits and risks. Benefits include a reduction in labour duration and a possible reduction in abnormal 5-minute Apgar scores. The meta-analysis provides no support for the hypothesis that routine early amniotomy reduces the risk of Cesarean delivery. Indeed there is a trend toward an increase in Cesarean section. An association between early amniotomy and Cesarean delivery for fetal distress is noted in one large trial. This suggests that amniotomy should be reserved for women with abnormal labour progress.