The Cochrane collaboration have updated their review on membrane sweeping for induction of labour (Finucane et al 2020).
This procedure, also known as a stretch and sweep, is offered to women in some parts of the world as the first step in the process of inducing labour.
There are good reasons that some clinicians and systems of care promote the ‘stretch and sweep’ intervention.
It is cheap and easy to perform and it can be done at home or in a clinic rather than in a hospital. Their hope is that it will prevent the need for labour to be induced with drugs and other interventions. This would be advantageous, as medical induction carries risks and is usually carried out in hospital.
But membrane sweeping is also controversial.
In some areas it is now offered routinely.
The pros and cons are often not discussed at length.
Some people feel that it is a good example of ‘too much intervention too soon’. It can imply that women’s bodies are inadequate.
And although many people agree that it is preferable to full-blown medical induction, there is an argument that we should be offering induction of labour only when the benefits truly outweigh the disadvantages.
What studies were included?
The review itself was updated as more studies have been published since the last edition. This edition includes 44 randomised studies.
These looked at the outcomes for 6940 women from a wide range of countries including high-, middle- and low-income countries.
The design of the studies varied, though. “Studies compared membrane sweeping with no intervention or sham intervention, and also compared membrane sweeping with vaginal or intracervical prostaglandins, oral misoprostol, oxytocin and repeated membrane sweeping.”
There were also some issues with possible bias: “Of the seven studies that reported financial funding, two studies reported funding from pharmaceutical companies. Overall, the certainty of the evidence was found to be low.” (Finucane et al 2020).
Previous research on this topic has suggested that membrane sweeping may be effective, but only in some women. And those might possibly be the women who were just about to go into labour anyway. That’s hard to measure, and most of the studies aren’t large enough to be able to assess that.
Let’s look a bit more closely at the numbers from this updated review.
Women who had membrane sweeping were a bit more likely to end up in spontaneous labour (and more on the use of this term below) than women who did not have membrane sweeping. But there isn’t a huge difference.
Without membrane sweeping, 598 women in 1000 will end up in spontaneous labour. (That’s about 6 in 10).
With membrane sweeping, 723 women in 1000 will end up in spontaneous labour. (So just over 7 in 10). (Finucane et al 2020).
The authors of the review state that, “Membrane sweeping may be effective in achieving a spontaneous onset of labour, but the evidence for this was of low certainty.” (Finucane et al 2020).
What about the effect on induction?
The authors also looked at whether having a membrane sweep reduced the chance that a woman would end up having her labour induced.
This is a slightly different question to the one above. One reason for that is because some women will have a caesarean after having a membrane sweep but before labour begins. Induction of labour is also a tricky outcome to measure because it isn’t a ‘naturally occurring’ outcome. It is the result of a decision.
It’s also possible that the decision may be influenced by whether or not the woman had a membrane sweep. Or by what the midwife or doctor felt when a membrane sweep was done. And the woman’s decision to accept or decline induction may be influenced by whether or not she had a membrane sweep and what happened afterwards.
In the new review:
Without membrane sweeping, 313 women in 1000 had their labour induced.
With membrane sweeping, 228 women in 1000 had their labour induced. (Finucane et al 2020).
The authors note that,“When compared to expectant management, it potentially reduces the incidence of formal induction of labour.” (Finucane et al 2020). Again, the difference isn’t huge and there will be other things to take into account.
Membrane sweeping and type of birth
There is another element of this area which is important, and this is highlighted several times by the authors of the updated review. When they analysed the results of the included studies, they found that membrane sweeping does not lead to a higher chance of having an unassisted vaginal birth. This is important, especially as we have seen some poor-quality studies and reviews which claim that induction reduces the chance of casarean section. But in studies of what really happens, induction actually increases the chance of intervention, including caesarean.
Membrane sweeping makes no difference to morbidity and mortality
This review was focused on whether membrane sweeping was effective in reducing induction of labour. But other outcomes are important too. So I want to mention the following important finding:
“We also found no clear differences between the groups for caesarean section, instrumental vaginal births or serious illness or death of the mother or baby.” (Finucane et al 2020).
Women’s views of membrane sweeping
The authors of this review are very clear that we do not have nearly enough evidence relating to women’s views on this topic. The evidence that they did find comes from just three of the 44 included studies. These studies suggests that women don’t mind membrane sweeping because they think the benefits outweigh the risks/discomfort. They would also recommend it to other women.
But it’s important to bear two things in mind. First, we don’t know what they were told about the risks and benefits. They may or may not have had accurate information – we can’t say. And second, the only women in these studies are those who were happy to have membrane sweeping. Those who didn’t want it or who had disliked having it in a previous pregnancy probably wouldn’t have agreed to be in the study.
So it’s good to know that some women are OK with it, but it’s also important that we ask this question of more women, and also seek to hear the voices of those who didn’t want to be in the studies, or whose experience wasn’t as good.
The question of spontaneous onset of labour
Another element of this review raises an important question. In common with some other authors on this topic, the authors talk about the possibility that women can go into spontaneous labour after a membrane sweep. But is this not a form of induction?
There is, as I mentioned above, some concern about these ‘milder’ interventions that are becoming routine. They may be being carried out by midwives, perhaps while having a nice chat at home or in the local clinic, but they are still interventions. And all interventions carry potential risks as well as potential benefits.
For example, women often report discomfort during and after membrane sweeping. Membrane sweeping can cause painful sensations which prevent them resting but don’t ‘put them into labour’. Infection is also a possibility. Another downside that we hear about occurs where a midwife or doctor accidentally breaks the baby’s waters. This means that the women will then be told she needs to be induced within the next day or two if she does not go into labour. This is because of concern about infection once the waters have been released.
Normalising interventions such as membrane sweeping can lead to a glossing over of the downsides. They can end up seeming like ‘just a small thing’ and yet they can have negative consequences. They can also undermine women’s confidence in their own bodies.
The individual’s decision
The final thing I want to mention is that any decision about induction of labour is, of course, a personal one.
If a woman isn’t keen to have a medical induction of labour, then she can say no to all interventions, including membrane sweeping. In many cases, membrane sweeping is offered (generally by kind-hearted birth attendants) in the hope of helping to avoid the more aggressive forms of induction of labour. But, as I have said elsewhere, it is entirely possible, legal and allowable to simply decline induction or any other intervention that you do not wish to have.
Our culture has become very focused on risk and prevention. As a result, intervention is often offered even when the risks are small and the likelihood of long-term negative consequences from the intervention is high. So it’s increasingly important that everyone gets good information in order to make the decisions that are right for them.
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