Membrane sweeping or membrane stripping is often mentioned at the end of pregnancy as a way of starting labour. It certainly sounds rather uncomfortable but what does it really involve and does it actually make any difference? Here are the facts to help you decide whether membrane sweeping is the right choice for you.
First, the physiology of membrane sweeping.
The very bottom of your uterus is called the cervix. The cervix sticks out slightly into the top of your vagina. When you aren’t in labour the cervix is pointing around towards your back rather than forwards directly towards the exit. This is good, because it reduces the risk of infections and damage to the cervix from anything entering the vagina.
The cervix is about 3cm long and has a firm consistency rather like the end of your nose. As it is 3cm long, it is like a tube with one entrance in your vagina and the other one opening into the uterus where the baby is.
The body is really clever and protects the baby from infection by filling this tiny tube with a mucousy jelly which catches any nasty bacteria trying to enter the uterus and cause an infection.
The baby is also surrounded by a bag of waters which sits against the lining of the uterus and protects the baby from infection, small bumps and jolts or pressure changes due to contractions.
The purpose of membrane sweeps
Although we don’t know lots about what starts labour, we do know that levels of natural prostaglandins rise in your body when labour begins. We also know that putting artificial prostaglandins up into the top part of your vagina can soften the cervix and start opening it up. These artificial prostaglandins are used as part of the induction of labour process at most hospitals when we want to start labour for any reason.
Natural prostaglandins can also be released by peeling the bottom part of the bag of waters gently away from the wall of the uterus. This is known as membrane sweeping or membrane stripping.
Research currently suggests that membrane sweeping can reduce the length of a pregnancy by about one week. This means women who have sweeps often go into labour earlier than they might have done without a sweep. If a sweep is successful, you are likely to go into labour within 48-72 hours of the process.
Policies differ between hospitals and care providers about when sweeps are offered and how many can be done for each woman. Please check with your midwife or health care provider for your local information.
The process of sweeping the membranes
Sweeping the membranes involves a vaginal examination. You will need to take off your underwear and lie down on the bed, covered with a sheet. Partners are welcome to stay with you, sitting at the head end of the bed and holding your hand if you wish.
The midwife or doctor will ask you to bring your ankles together and your heels up towards your bottom so that your knees bend. You will then be asked to let your knees flop open to either side.
The midwife will then insert two fingers of her gloved hand into your vagina using lubricating jelly to reduce the discomfort. She will need to reach the cervix, so if it is still pointing towards your back, she may ask you to put your hands into fists and put them under your bottom. This tilts your pelvis and makes it easier to reach a cervix that is pointing backwards.
When the midwife reaches the cervix with her fingers, she will try to put her finger through the tube of the cervix and into the uterus, where she will be able to feel the baby’s head through the bag of waters! She will then move her finger in a circular motion between the bag of waters and the wall of your uterus. When she does this, she peels the bag away from the wall which makes the body release natural prostaglandins.
What happens if membrane sweeping isn’t possible?
Sometimes, the midwife may not be able to reach the cervix. In other cases, the cervix may be so tightly closed that she can not reach through it to get to the bag of waters and sweep it away from the wall of the uterus. Unfortunately, we don’t know what we will find until we try. However, if the midwife can’t reach the cervix or through it to the uterus, giving the cervix and the area around it a gentle massage with her fingers may be helpful in softening and stretching the fibres of the cervix. This may make it more responsive to any tightenings or contractions you may have. It may also start the cervix softening so that in another few days the cervix is open enough to sweep the membranes.
After the membrane sweep
Once the examination is over, you may notice some heavier vaginal discharge, so it’s worth bringing a maternity pad with you to your appointment to wear home. You may also note a tinge of blood in the discharge. This is very common as when the midwife puts her fingers through the cervix it opens slightly more and small blood vessels called capillaries break. This bloody discharge should only be a small amount, so please contact your care provider if it seems heavy to you or you are worried.
It’s important to stay as upright and as active as possible after a membrane sweep. This pushes baby’s head down onto your cervix, which will already have been stimulated by the sweep. More stimulation will help your body produce more prostaglandins and start the hormone oxytocin flowing. Oxytocin causes contractions, which is exactly what we want! Perhaps try a good long walk, or bounce around the house on a birthing ball.
While you wait for the membrane sweep to work, why not read some of my other posts? You can find out my top tips for early labour here. The NHS website also has great information on induction of labour and choices when labour reaches 41 weeks. Read that here.