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Last week, we talked about how difficult it is to be pregnant during hot summer weather. This past week has been cooler, which has made things a little easier. However, many women still come to the clinic wanting to give birth. They are tired, experiencing pelvic pain, and having trouble sleeping. To expedite the onset of labor, we sometimes perform a procedure called membrane sweeping.
However, I wonder about the scientific evidence behind what we are doing.
Membrane Sweeping
Membrane sweeping is a technique that often comes up in my clinical practice at the hospital. Membrane sweeping seems to be very popular.
Many of the women I meet have visited their midwife at the Maternal and Child Health Center (MVC) and say they have had their membranes swept, sometimes up to 3-4 times in a short period. Many describe having uncomfortable cramps afterward, but not much more. Others claim that it kick-started their labor.
So, my question is whether they would have gone into labor anyway, even without membrane sweeping. Or does it have a proven effect?
Therefore, I have delved a bit deeper into the subject. Is this evidence-based science we are dealing with, or is it more based on opinions? We must not forget that simply "doing something" has an impact, regardless of what it is. It's the psychological aspect of healthcare.
What is required to perform a membrane sweep?
The term used in English is "membrane sweep" or "membrane stripping." According to the literature, midwives have been using this method for a long time and have considered it a simple way to attempt to initiate labor.
To perform a membrane sweep, the cervix must be ripe. Within obstetric care, we often emphasize the concept of cervical ripening. A ripe cervix means that it becomes softer, changes position (facing forward), and starts to dilate. This is how the body prepares for spontaneous labor.
To perform a membrane sweep, the cervical opening (both external and internal) must be at least one finger wide. Otherwise, it would not be possible to reach the fetal membranes, which are the ones that are "swept." The requirements also include a normal pregnancy with the fetus in a head-down position and intact fetal membranes.
It is also important that the woman understands what we are doing and gives her consent. We have had cases at the clinic where women have read their birth records afterward and discovered that they were "membrane swept," something they were not aware of. Several women have been very upset about this. Many also find it uncomfortable and painful.
What is a membrane sweep, and what effect is it believed to have?
During a vaginal examination, the examiner inserts one or two fingers into the cervix, up to the internal os, and makes circular movements with their finger(s) to gently detach the fetal membranes from the lower part of the uterine lining.
The belief is that the membrane sweep stimulates the release of a group of hormones called prostaglandins. Prostaglandins have a close association with the initiation of labor itself, which has been scientifically proven in many studies. Prostaglandins help soften the cervix and initiate the possibility of regular contractions later on.
Risks and Benefits
The risks associated with membrane sweeping are considered small. If the fetal membranes are intact, the risk of infection, for example, is minimal. However, there is a small risk of bleeding due to the presence of fragile blood vessels in and around the cervix. This bleeding, however, is not dangerous.
Another effect is the experience of cramps. While these cramps can be painful, they do not lead to labor. The biggest risk, therefore, is that nothing happens. Many women are disappointed in such cases.
Research Findings
A search of current databases yields around 5 million results, indicating that this is a topic that has been extensively studied, and membrane sweeping is a widespread and established procedure in obstetrics.
However, we still need more scientific knowledge and understanding of what we are doing. Foreign sources, as well as our general perception in Sweden, suggest that membrane sweeping reduces the risk of induction with medication. It is also claimed that membrane sweeping increases a woman's chance of spontaneous vaginal delivery.
Disadvantages mentioned include pain during the procedure, the risk of bleeding and membrane rupture leading to an infection, as well as irregular and ineffective contractions (cramps) that can bother the woman.
Cochrane Meta-Analysis
In my search, I found a meta-analysis from the Cochrane Library (the most trusted international database for comparing and establishing research results), conducted as recently as 2020, focusing on membrane sweeping (Membrane sweeping for induction of labor).
The analysis includes 44 randomized controlled trials involving a total of 6,548 women. Membrane sweeping was performed in the intervention group, and the results were compared to no membrane sweeping in the control group.
Unfortunately, the number of women in the various studies is very small, which makes the results more uncertain. Many of the studies are also quite old (the earliest published in the 1970s).
The results show an increased occurrence of spontaneous onset of labor in the intervention group. However, it shows no difference in the mode of delivery, i.e., the rate of cesarean sections. There were also no differences in outcomes for the mother and baby.
Unfortunately, this Cochrane analysis has a low level of evidence.
The studies were small, and there was a significant difference between the countries where the studies were conducted. Some were from Europe/USA, while others were from third-world countries like Africa. Comparing them is difficult as they were conducted differently, resulting in a low level of evidence.
Should we continue with membrane sweeping in Swedish obstetrics?
What does this mean for us in obstetric care in Sweden? We can conclude that we still do not know if what we are doing is beneficial or not.
In the Swedish multicenter study named "Swepis," they compared the outcomes of going past the due date by one or two weeks. It was concluded that giving birth no later than week 41, i.e., one week overdue, was safest for the mother and baby.
This study has probably contributed to membrane sweeping becoming even more popular in our country. We are trying to help women, but honestly, we do not know if we are doing them a favor or a disservice.
My opinion is that we should conduct a large randomized study where we carefully calculate the number of women to be included in the different groups to provide a reliable answer and also examine any complications.
This should be done soon. So far, we are doing something without knowing for sure if it is effective or not. Scientific evidence is lacking. In my view, this seems rather unscientific.
To be continued.
/Doctor Eva