A Cochrane review included 22 trials and 2797 women, 20 comparing sweeping of membranes with no treatment (2389 women), three comparing sweeping with prostaglandins and one comparing sweeping with oxytocin. Risk of caesarean section was similar between groups (RR 0.90, 95% CI 0.70 to 1.15). Sweeping of the membranes was associated with reduced duration of pregnancy and reduced frequency of pregnancy continuing beyond 41 weeks (RR 0.59, 95% CI 0.46 to 0.74) and 42 weeks (RR 0.28, 95% CI 0.15 to 0.50). To avoid one formal induction of labour sweeping of membranes must be performed in eight women (NNT = 8). There was no evidence of the risk of maternal or neonatal infection. Discomfort during vaginal examination and other adverse effects (bleeding, irregular contractions) were more frequently reported by women allocated to sweeping.
In an RCT 742 low-risk pregnant women were randomly assigned to serial sweeping of the membranes (every 48 hours until labour commenced up to 42 weeks of gestation) or no intervention. In the sweeping group the risk of post-term (> 42 weeks) pregnancy was decreased (23% vs 41%; RR 0.57, 95% CI 0.46 to 0.7 1; NNT 6) and this benefit was seen both in nulliparous and parous women. Obstetric outcomes and indicators of neonatal morbidity, and adverse effects were similar in both the groups except for uncomplicated bleeding, which was reported more frequently in the sweeping group.