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

Abstract

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

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

Methods: 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.

Results: 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).

Conclusion: 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.

Keywords: Bishop’s score; labor induction; postmaturity pregnancy; pregnancy duration.

Figure 1

Flow diagram of the randomized controlled trial of membrane sweeping frequency. Abbreviation: n, number.

Figure 2

Kaplan–Meier survival curves comparing the time interval between randomization and delivery. Overall and pair-wise log-rank tests were performed to assess the equality of survivor functions. Note: The results of the survival curve indicate that there were no significant differences between the three groups (P = 0.081).