Does amniotomy shorten spontaneous labor or improve outcomes?
EVIDENCE-BASED ANSWER:
No. Amniotomy neither shortens spontaneous labor nor improves any of the following outcomes: length of first stage of labor, cesarean section rate, maternal satisfaction with childbirth, or Apgar score <7 at 5 minutes (strength of recommendation [SOR]: A, large meta-analyses of randomized controlled trials [RCTs] and a single RCT with conflicting results).
Amniotomy does result in about a 55% reduction of pitocin use in multiparous women, a small (5 minutes) decrease in the duration of second-stage labor in primiparous women, and about a 50% overall reduction in dysfunctional labor—ie, no progress in cervical dilation in 2 hours or ineffective uterine contractions (SOR: A, large meta-analyses of RCTs and a single RCT with conflicting results).
Amniotomy doesn’t improve other maternal outcomes—instrumented vaginal birth; pain relief; postpartum hemorrhage; serious morbidity or death; umbilical cord prolapse; cesarean section for fetal distress, prolonged labor, antepartum hemorrhage—nor fetal outcomes—serious neonatal morbidity or perinatal death; neonatal admission to intensive care; abnormal fetal heart rate tracing in first-stage labor; meconium aspiration; or fetal acidosis (SOR: A, large meta-analyses of RCTs and a single RCT with conflicting results).
Three trials (1695 women) evaluated dysfunctional labor, defined as no progress in cervical dilation in 2 hours or ineffective uterine contractions. Amniotomy reduced dysfunctional labor in both primiparous (RR=0.49; 95% CI, 0.33-0.73) and multiparous women (RR=0.44; 95% CI, 0.31-0.62).
No differences found in other maternal and fetal outcomes
Investigators reported no differences in other secondary maternal outcomes: instrumental vaginal birth (10 trials, 5121 women); pain relief (8 trials, 3475 women); postpartum hemorrhage (2 trials, 1822 women); serious maternal morbidity or death (3 trials, 1740 women); umbilical cord prolapse (2 trials, 1615 women); and cesarean section for fetal distress, prolonged labor, or antepartum hemorrhage (1 RCT, 690 women).
Investigators also found no differences in secondary fetal outcomes: serious neonatal morbidity or perinatal death (8 trials, 3397 women); neonatal admission to neonatal intensive care (5 trials, 2686 women); abnormal fetal heart rate tracing in first stage of labor (4 trials, 1284 women); meconium aspiration (2 trials, 1615 women); and fetal acidosis (2 trials, 1014 women). Similarly, 1 RCT (39 women) that compared amniotomy with intent to preserve membranes in spontaneous labors that became prolonged found no difference in cesarean section, maternal satisfaction, or Apgar scores.
A few studies claim shorter labor with amniotomy
However, a later Iranian RCT (300 women) reported that early amniotomy shortened labor (labor duration: 7.5 ± 0.7 hours with amniotomy vs 9.9 ± 1.0 hours without amniotomy; P<.001) and reduced the risk of dystocia (RR=0.81; 95% CI, 0.59-0.90) and cesarean section (RR=0.82; 95% CI, 0.66-0.90).2
A similar Nigerian RCT (214 women) and an Indian RCT (144 women) both claimed that amniotomy also shortened labor (4.7 ± 0.9 hours vs 5.9 ± 1.3, and 3.9 ± 2 hours vs 6.1 ± 2.8 hours, respectively).3,4 In neither trial, however, did investigators explain how the difference was significant when the duration of labor times overlapped within the margin of error.
