Amniotomy During Spontaneous Labor Benefits Neither Mother Nor Child

LIVERPOOL, England, Oct. 17 -- Amniotomy during a spontaneous birth did not reduce the time of labor or improve the condition of the newborn, according to a systematic review of the literature.

There was no evidence of any statistical difference in the length of the first or second stage of labor, maternal satisfaction with the experience, or the infant's Apgar score, Rebecca Smyth of the University of Liverpool, and colleagues, wrote in an online Cochrane Review report.

At this time, they said, amniotomy should not be used without good clinical reason as part of standard labor management and care.

Intentional rupture of the amniotic membranes during labor is one of the most commonly performed procedures in modern obstetric and midwifery practice, they pointed out. The primary aim is to speed contractions, thereby shortening the length of labor.

Rupturing the membranes is thought to release hormones and chemicals that stimulate contractions and speed the pace of labor, the reviewers said.

However, there is little evidence that a shorter labor has benefits for either mother or child, and there are several potential risks, albeit rare, including problems with the umbilical cord and the baby's heart rate, the reviewers said.

The reviewers searched the Cochrane pregnancy and Childbirth Groups' trial register up to March 30, 2007.

Fourteen randomized controlled trials, including 4,893 women, compared amniotomy alone versus intention to preserve the membranes (the control group). None of the studies assessed whether amniotomy increased women's pain during labor.

There was no evidence of any statistical difference in length of first stage of labor (weighted mean difference -20.43 minutes, 95% confidence interval 95.93 to 55.06).

There was also no statistically significant difference in the length of the second stage of labor between the two groups (weighted mean difference -2.38, CI -5.27 to 0.50).

When examining subgroups of primiparous women only and multiparous women only, again, there were no statistically significant differences, the reviewers found.

Nor were there significant differences for maternal satisfaction with the childbirth experience (standardized mean difference 0.27, 95% CI -0.49 to 1.04) and low Apgar scores, less than seven at five minutes (RR 0.55, CI 0.29 to 1.05).

Women in the amniotomy group tended to have an increased risk of a suboptimal or abnormal fetal heart trace, although the difference was not statistically significant (RR 1.09, CI 0.97 to 1.23).

Information on maternal satisfaction came from only two trials including 123 women. The reviewers called this lack of information disappointing, given that 10 of 14 trials were published in 1990 and later.

However, amniotomy was associated with a tendency toward increased risk of delivery by caesarean section compared with the controls, although the difference was not statistically significant (RR 1.26, CI 0.98 to 1.62).

Finally, the reviewers said, there was no consistency between studies regarding the timing of amniotomy during labor in terms of cervical dilatation.

These results, the reviewers said, should be interpreted with caution. In eight out of the 14 reports, 31% to 60% of women randomized to the non-amniotomy control group received an amniotomy at some stage in their labor.

All data in the review were presented by "intention to treat" and not by the intervention actually received. This may have influenced the conclusions, the reviewers said.

The reviewers called for multicenter randomized controlled trials with clear allocation concealment, which would allow for robust conclusions. It is of note, they said, that the largest trial in this review, a multi-center trial, involved only 1,463 women.