Objective: To determine whether weekly sweeping of the membranes from 39 weeks of gestation results in a reduction in the number of women reaching 41 completed weeks and subsequently in a reduction of the number of women who will need induction of labour.
Design: Randomised controlled trial.
Participants: Two hundred and seventy-eight nulliparous women, who were seen at the antenatal clinic of a university teaching hospital, were randomly allocated at 39 weeks of gestation to receive on a weekly basis either sweeping of the membranes (n = 140) or a routine pelvic examination (n = 138).
Main outcome measures: The time interval between randomisation and delivery, the incidence of prolonged pregnancy (i.e. > 41 completed weeks), and the incidence of induction of labour.
Results: In 24 women (17%) sweeping of the membranes was not possible. Fifty-three women (38%) in the sweeping group and 50 women (36%) in the control group were delivered within one week after randomisation. Women allocated to sweeping showed a trend towards having a shorter randomisation-delivery interval: 9.4 days versus 10.6 days in the controls (P = 0.087). Sweeping had no statistically significant effect on the mean duration of pregnancy (282.8 days in the sweeping group versus 283.8 days in the control group, P = 0.127). The need for induction of labour was significantly reduced in those women who underwent sweeping (11% versus 26%, P = 0.004), merely as a result of a decrease in the number of women that exceeded 41 weeks (19% versus 33%, P = 0.016).
Conclusion: Sweeping of the membranes weekly from 39 weeks does not increase the number of women who will deliver within the first week but significantly decreases the number that will reach 41 weeks. Induction of labour then becomes less necessary.