Findings. Women randomly assigned to early amniotomy had a similar risk of CD compared with controls (31.1% vs 30.9% [relative risk (RR), 1.05; 95% confidence interval (CI), 0.71–1.56]) and a shorter interval from induction to delivery of about 5 hours (mean difference, -4.95 hours [95% CI, -8.12 to -1.78]).
There was no difference in any of the secondary outcome measures, although the number of events was small. Specifically, there was no significant difference in rates of chorioamnionitis between the early and late amniotomy cohorts (7.3% vs 4.8% [RR, 1.47; 95% CI, 0.95–2.28]).
Study strengths and limitations
This is the first systematic review to evaluate early versus late amniotomy after cervical ripening for induction of labor. “Systematic review and meta-analysis” is not synonymous with a review of the literature. It has its own methodology and is regarded as original research. A strength of this study is that it was performed by a highly credible team who followed established Cochrane and PRISMA methodological and reporting guidelines.
Study weaknesses include the fact that the meta-analysis contained a relatively small number of trials and study participants. It was significantly underpowered to address issues related to neonatal outcome. The 4 trials included were highly variable in terms of maternal parity and indications for labor induction and CD. The definition of “early amniotomy” was inconsistent, and the overall rate of CD varied greatly among the studies (7.9%–41.1%). Multiple pregnancies were excluded. Taken together, these findings may have limited generalizability.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
This is the first systematic review to evaluate early versus late amniotomy/spontaneous rupture of membranes after cervical ripening for induction of labor. The study results suggest that amniotomy soon after cervical ripening does not change the likelihood of CD, but it does shorten the induction-to-delivery interval by around 5 hours. Prior studies have shown that early amniotomy in women in spontaneous labor decreases time to delivery by an average of 3 hours.4 Now we know that this is true also of early amniotomy following cervical ripening for induction of labor.
A number of questions still remain before early amniotomy is introduced into routine practice: Does group B streptococcus colonization status matter? Does this practice increase the risk of chorioamnionitis? At this time, it seems most prudent to individualize amniotomy timing based on a woman's obstetric history, indication for induction, and response to cervical ripening.
ERROL R. NORWITZ, MD, PHD, MBA, AND DIANA KOLETTIS, MD