The words stretch and sweep when combined to describe a pre-labour procedure are enough to make any pregnant woman’s eyes water.
But while most of us have heard of the procedure, few of those who haven’t experienced a stretch and sweep would know exactly what to expect from the process.
Here, obstetrician Dr Brad Robinson answers the most commonly asked questions regarding this relatively common labour-inducing technique.
Far from a medieval torture technique as it name may suggest to some, a ‘stretch and sweep’ is the colloquial term for membrane stripping which is used as a form of induction of labour.
Also called a ‘strip and stretch’, it describes the process whereby the obstetrician does a vaginal examination and, using his fingers, attempts to stretch and expand the area inside the pregnant woman’s cervix. If the cervix is open enough, the examiners finger is inserted through the patient’s cervix and rotated circumferentially in each direction. This results in separation of the fetal membranes from the inner uterine lining, and – hopefully – results in the onset of labour.
This technique can result in labour by two mechanisms. Firstly, mechanically performing this stretching causes the release of hormone-like compounds called prostaglandins from the membranes, uterine lining and cervix. Prostaglandins are intimately associated with the onset and progression of labour. Secondly, it can result in direct dilation of the mother’s cervix.
This procedure is one of the forms of induction of labour in an obstetrician’s armamentarium, along with prostin gels and tapes and mechanical dilation with specialised catheters.
There is no specific time when a strip and stretch should be performed. Indeed, there is a lot of variability about if and when different women want it done. Some run a mile at the suggestion, while others practically beg for it to be performed, as they are keen to try anything to bring their pregnancy to a close!
Having said that, it is typically performed as close to full term as possible so as to increase its likelihood of success. In order to do the strip and stretch the cervix needs to be partially dilated, so this is one of the factors that restrict its performance before the very late stages of pregnancy.
A strip and stretch involves performing a vaginal examination and then mechanically stretching the inner aspect of the lower uterine segment. So, if an obstetrician is able to perform this without causing discomfort, I would suggest to you that they could be found to also be able to walk on water and divine for water using a pair of rusty forceps.
So some level of discomfort is a given. However, sweeping of the membranes should not be abjectly painful. Indeed, if the patient finds it too uncomfortable then it can and should be immediately ceased. However, some women are so eager to bring on their labour that they are prepared to tolerate the discomfort that this procedure can sometimes bring!
It does stand to reason that a more vigorous stretch and sweep is more likely to result in the release of more prostaglandins, and cause more cervical dilatation, and therefore be more likely to succeed. When I was training in obstetrics and gynaecology one of my more senior colleagues was renowned for his great success with strip and stretches. When asked why he was so successful, this clinician of few words simply said, “Two fingers, rotated each direction, three times”.
This procedure is not performed on every patient who enters the later gestations of pregnancy, however, it is certainly not uncommon. There is a lot of variability over women’s attitudes towards it, with some loving its potential for bringing on labour, while others would gladly risk the pregnancy continuing and decline its performance.
Generally speaking, for women whom are presenting for antenatal review in or around their 40th week of pregnancy a discussion is had about membrane sweeping and its likelihood of success. Reasons for it not being performed commonly include a patient’s concern about its discomfort or its efficacy, and also the cervix not being sufficiently dilated.
Studies show that if a patient has weekly membrane stripping performed this does reduce the amount of time for them to enter labour spontaneously when compared to doing nothing. It also reduces the need for the patient to have a formal induction of labour.
A recent comprehensive analysis found that membrane sweeping:
While these findings paint an impressive picture for membrane sweeping, it can be contextualised by considering that eight women need to undergo a strip and stretch for just one to avoid having an induction of labor.