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As you approach your due date, you may be offered “membrane sweeping,” a.k.a., “membrane stripping,” a procedure in which your doctor or midwife lifts the amniotic sac off the cervix during a vaginal exam. The theory is that the resulting irritation is a harmless way to stimulate labor to start sooner than it otherwise would. That’s probably going to sound like a good idea, given how you’re likely to be feeling at that point in your pregnancy. Is it?

In this article we’ll see what the research has to say on whether it is, in fact, 1) effective, and 2) harmless, and as usual, I’ll provide you a “takeaway” section with practical suggestions about what you can do with what you’ve learned.

Is Membrane Sweeping Effective?

The best evidence for effectiveness comes from a systematic review pooling data from multiple randomized controlled trials, studies in which participants were assigned either to undergo membrane sweeping or not by chance, the latter being the control group (Finucane 2020). At first glance, it looks like membrane sweeping is effective. Among the trials reporting on the percentage beginning labor spontaneously (3,170 participants in all), 72 percent in the membrane sweeping group had labor start on its own versus 60 percent of the control group, and statistical analysis showed that the difference was unlikely to be due to chance. Membrane sweeping also forestalled induction among the trials reporting on this outcome (3,224 participants in all): 23 percent were induced in the membrane sweeping group versus 31 percent of the control group, and this difference, too, was unlikely to be due to chance. So far, so good. But there’s a catch: when the analysis was limited to the higher quality studies, differences in rates of spontaneous labor onset (65% vs. 60%) and induction of labor (27% vs. 30%) were much smaller, and statistical analysis showed that the difference was likely to be due to chance.

There’s another problem too: the main point of trying to get labor going sooner and of inducing labor when that doesn’t work is to reduce cesareans. But whether you look at the pooled data from all studies or just from the high-quality studies, membrane sweeping had no effect on cesareans. And there’s more: a secondary reason for curtailing pregnancy is to prevent a stillbirth or severe adverse outcome that might have occurred had the pregnancy been allowed to continue, and membrane sweeping had no effect on these occurrences either.

Is Membrane Sweeping Harmless?

So far, we’ve learned that membrane sweeping has no benefits other than possibly triggering labor with less medical intervention than involved in a formal labor induction. That makes its potential harms all the more important to consider.

Reporting on possible harms, the review found that membrane sweeping didn’t increase probability of excessive postpartum bleeding, or, as you saw above, of severe adverse outcomes in babies (Finucane 2020). One potential harm not evaluated in the systematic review, however, is whether membrane sweeping provokes the amniotic sac breaking. This is a concern because should that happen, you’re almost certainly looking at an earlier delivery than nature intended either from contractions starting up their own or because your care provider induces labor if they don’t. What does the research have to say about this?

An earlier systematic review looked at this issue and concluded membrane sweeping didn’t affect rupture of membranes (Boulvain 2005), but there’s a catch here too: it’s common policy that if the cervix isn’t sufficiently open to permit membrane sweeping, to massage the cervix instead. A different trial found that among those whose cervixes were tightly closed (which would mean that if they were in the sweep group, they would have had cervical massage), membrane release before labor onset occurred at similar rates to the control group (Hill 2008). However, among trial participants who had cervixes open enough to permit the procedure, 9 percent in the membrane sweep group had membranes release prior to labor versus no one in the control group. So, in answer to the question of whether membrane sweeping is harmless, it may increase the probability of membrane rupture prior to labor onset, which might lead to an avoidable labor induction or to earlier onset of labor than would have happened naturally.

Your Takeaway

If you’ve decided to decline a membrane sweep, be sure to let your care provider know at every late pregnancy visit. Some care providers may just go ahead and perform one during a vaginal exam without asking permission first.

On the other hand, the possibility of jump starting labor may be of advantage to you. For example, if you are planning birth at home or at a freestanding birth center, you may lose that option if your pregnancy goes beyond the beginning of week 41. I have argued elsewhere why this shouldn’t be so in an otherwise healthy pregnancy, but nonetheless, state birth regulations may require it. And, of course, you may decide that you’re just that miserable that you want a membrane sweep. Now, though, you’ll be making an informed decision about it.

References

Boulvain M, Stan C, Irion O. Membrane sweeping for induction of labour. Cochrane Database Syst Rev 2005(1):CD000451.

Finucane EM, Murphy DJ, Biesty LM, et al. Membrane sweeping for induction of labour. Cochrane Database Syst Rev 2020;2(2):CD000451.

Hill MJ, McWilliams GD, Garcia-Sur D, et al. The effect of membrane sweeping on prelabor rupture of membranes: a randomized controlled trial. Obstet Gynecol 2008;111(6):1313-9.