Membrane sweeping and prevention of post-term pregnancy in low-risk pregnancies: a randomised controlled trial.

OBJECTIVE: To evaluate the effectiveness of membrane sweeping at 41 weeks for the prevention of post-term pregnancy.

DESIGN: A multicentre randomised controlled trial.

SETTING: Fifty-one primary care midwifery practices in the Netherlands.

POPULATION: A total of 742 low-risk pregnant women at 41 weeks of gestation.

METHODS: Participants were randomly assigned to serial sweeping of the membranes (every 48 hours until labour commenced up to 42 weeks of gestation) or no intervention.

MAIN OUTCOME MEASURES: Post-term pregnancy (>or=42 weeks). Subgroup analyses were performed on nulliparous and parous women. Secondary outcomes included adverse effects.

RESULTS: Serial sweeping of the membranes at 41 weeks decreased the risk of post-term pregnancy (87/375 [23%] versus 149/367 [41%]; relative risk [RR] 0.57, 95% CI 0.46-0.71; number needed to treat [NNT] 6 [95% CI 4-9]). Benefits were also seen in both subgroups (nulliparous: 57/198 [29%] versus 89/192 [46%]; RR 0.62 [95% CI 0.48-0.81]; NNT 6 [95% CI 4-12] and parous: 30/177 [17%] versus 60/175 [34%]; RR 0.49 [95% CI 0.34-0.73]; NNT 6 [95% CI 4-6]). Adverse effects were similar in both the groups except for uncomplicated bleeding, which was reported more frequently in the sweeping group. Other obstetric outcomes and indicators of neonatal morbidity were similar in both groups. There were two perinatal deaths in each group.

CONCLUSIONS: Membrane sweeping at 41 weeks can substantially reduce the proportion of women with post-term pregnancy.