Randomized clinical trial evaluating the frequency of membrane sweeping with an unfavorable cervix at 39 weeks

Despite the widely accepted use of membrane sweeping to prevent postmaturity pregnancies, the optimal frequency for this procedure has not been established.

To determine if the frequency of membrane sweeping in women with an unfavorable cervix at term results in fewer labor inductions.

This was a randomized trial of women with an unfavorable cervix (Bishop's score of ≤4) at 39 weeks randomized into three groups: control, once-weekly membrane sweeping, and twice-weekly membrane sweeping.

Between January 2005 and June 2008, 350 women were randomized into the study (groups: control [n = 116], once weekly [n = 117], and twice weekly [n = 117]). Randomization of Bishop's score was different between groups (P = 0.019), with 67%, 71%, and 83% of control, once-, and twice-weekly groups, respectively, having scores of 3-4. There was no difference in the unadjusted rate of labor induction between the groups (35% versus 27% versus 23%, P = 0.149), and after the adjustment for the randomization of Bishop's score (adjusted odds ratio [OR] = 0.73, 95% confidence interval [CI] 0.41-1.29 and OR = 0.65, 95% CI 0.36-1.18 for once- and twice-weekly groups, respectively). A Bishop's score of 3-4 at randomization was the only statistically significant factor that decreased the likelihood of induction at 41 weeks (OR = 0.42, 95% CI 0.25-0.69).

Frequency of membrane sweeping does not influence the likelihood of remaining undelivered at 41 weeks of pregnancy. The Bishop's score at around 39 weeks is the important factor as a predictor of the duration of pregnancy, and further studies would be required to determine whether membrane sweeping influences pregnancy duration.