Membrane Sweeping and Prevention of Post-Term Pregnancy in Low-Risk Pregnancies: A Randomized Controlled Trial

Postterm pregnancy, defined as a gestational age of 42 weeks or longer, has been associated with increased perinatal morbidity and mortality. “Sweeping” the membranes—separating them digitally from the lower urine segment—is a simple means of promoting spontaneous labor presumably by increasing prostaglandin levels in the maternal circulation as well as local prostaglandin production. Both of these effects help to ripen the cervix. However, trials of membrane sweeping have yielded inconsistent results. This randomized trial evaluated membrane sweeping starting at 41 weeks gestation in 51 midwifery practices in The Netherlands. All participants had a single fetus in cephalic presentation and lacked pregnancy complications and risk factors. The lower membranes were separated to the extent possible from their cervical attachment sites using 3 passes of the examining fingers. When the cervix was closed, precluding sweeping, it was massaged. Sweeping was repeated every 48 hours a maximum of 3 times until labor began or gestational age reached 42 weeks. Of 742 women admitted to the trial, 375 were allocated to membrane sweeping and 367 to a control group. The 2 groups were similar at the outset. Sweeping significantly lowered the proportion of postterm pregnancies from 41% to 23%. Results were unchanged when only women dated by a first-trimester ultrasound study were analyzed. In the group having membrane sweeping, 27% of women with a Bishop score less than 6 at baseline and 9% of those with an index of 6 or higher had postterm pregnancies. Sweeping reduced the interval between randomization and delivery by 1 day on average, and it significantly increased the chance of spontaneous labor starting before 42 weeks gestation. Both nulliparous and parous women benefitted from the procedure. In parous women, sweeping made it significantly more likely that delivery would take place in a primary care setting. Women having membrane sweeping were less likely to receive prostaglandins to induce labor. Adverse effects were similarly frequent in the 2 groups except for more frequent bleeding in those assigned to membrane sweeping. A majority of women felt that the procedure was “somewhat” painful and 17% found it to be “painful” or “very painful.” Nearly 90% of women would choose membrane sweeping in their next pregnancy. Sweeping the membranes at 41 weeks gestation can be expected to considerably lower the risk of a postterm pregnancy at 42 weeks or later. It is a simple technique that does not require hospital admission.