The effectiveness of sweeping membranes at term: a randomized trial

Abstract

Objective: To determine whether sweeping or stripping membranes at 38-40 weeks' gestation leads to spontaneous labor within 7 days.

Methods: One hundred fifty antenatal low-risk patients at 38-40 weeks' gestation were assigned randomly to sweeping or control (ie, Bishop score only) groups and stratified based on the ability to pass a finger through the internal os. The primary outcome was the rate of spontaneous labor within 7 days. Major secondary outcomes included the spontaneous labor rate before 41 weeks and the overall spontaneous labor rate. Other outcomes included maternal and neonatal morbidity. The sample size was calculated based on doubling of the spontaneous labor rate within 7 days from 28% to 56% (alpha = 0.05, beta = 0.10).

Results: The subjects were demographically similar between the groups. There were no differences between the groups in the primary outcome of spontaneous labor within 7 days (33% sweeping, 38% control; P = .39) or in the secondary outcomes of spontaneous labor before 41 weeks (P = .66) or the overall spontaneous labor rate (P = .09). The Bishop score predicted spontaneous labor within 7 days (P = .003), and gestational age at enrollment predicted spontaneous labor before 41 weeks (P = .008) and the overall spontaneous labor rate (P = .008), using logistic regression to control for potential confounders.

Conclusions: Sweeping membranes once at 38-40 weeks' gestation does not significantly increase the proportion of women who begin spontaneous labor within 7 days.