The membrane sweep, also known as stripping the membranes, is a mechanical procedure performed near the end of pregnancy to encourage the onset of labor. During a routine internal examination, a healthcare provider inserts a finger through the cervix and gently separates the amniotic sac from the lower wall of the uterus. This action stimulates the natural release of prostaglandins, hormones that help ripen the cervix and prepare the body for delivery. The goal of this intervention is to promote spontaneous labor, potentially helping patients avoid a medical induction.
The Typical Timeline for Labor Onset
Labor most often begins within 24 to 72 hours of the membrane sweep. Research suggests that approximately 70% of low-risk women who undergo the procedure will eventually go into spontaneous labor. A study found a 24% increased chance of going into labor within 48 hours following a sweep, and a 46% increase in the chance of delivering within a week. For example, one review showed that 90% of women who received a sweep delivered by 41 weeks, compared to 75% of those who did not.
Factors Influencing Sweep Success
Cervical Readiness (Bishop Score)
The success of a membrane sweep depends highly on the pre-existing readiness of the mother’s body. The most important factor is the condition of the cervix, which is assessed using the Bishop Score. This scoring system evaluates components including cervical dilation, effacement (thinning), consistency, and position. A Bishop Score of six or higher is considered a favorable condition, suggesting the cervix is already soft and prepared for labor.
Gestational Age and Parity
The procedure is more likely to be effective when performed at or beyond 40 weeks gestation. A patient’s parity, or the number of previous times they have given birth, is another strong indicator of potential success. Multiparity is a factor for successful delivery because the cervix has already undergone softening and opening in a prior pregnancy.
What to Expect Immediately After the Sweep
In the hours immediately following the membrane sweep, it is common to experience physical sensations that do not necessarily mean true labor is starting. Most individuals will notice cramping or a dull ache in the lower abdomen, similar to menstrual cramps. This cramping results from the physical manipulation of the cervix and the release of prostaglandins. Light vaginal bleeding or spotting, often called “bloody show,” is also common and may include the loss of the mucus plug.
Irregular contractions, such as Braxton Hicks, may become more noticeable but often remain sporadic and do not increase in intensity. It is important to differentiate these expected symptoms from the signs of established labor. True labor contractions will build in frequency, duration, and intensity, making it difficult to talk or walk through them. A healthcare provider should be contacted immediately if a patient experiences heavy, bright red vaginal bleeding that soaks through a pad, or if the membranes rupture.