Cervical dilation (often just called dilation) is the process in which your cervix (the ‘neck’ of your womb that joins to the top of your vagina) opens during labour so that your baby can pass through to be born.
We know that as your due date approaches you’ll probably have lots of questions around this issue. So we’ve asked our expert GP, Dr Philippa Kaye, to answer some common queries on when dilation happens, what it feels like, how long it takes, and what all the talk about ‘closed’ and ‘effaced’ and various ‘centimetres’ means…
1. When does cervical dilation happen?
“For most women, it happens when you are at full term and ready to go into labour,” says Dr Philippa. “This means between 37 and 42 weeks of pregnancy, with the end of week 40 being your due date.
“If you go beyond your due date and haven’t delivered by 41 weeks of pregnancy, you are likely to be booked for induction of labour before the end of the 42nd week. If you go into labour before 37 weeks, it would be considered a preterm delivery.”
Dilation is preceded by something call ‘effacement’ (or, in years gone by, ‘ripening’) – where your normally tightly closed cervix stretches, softens and thins – and the mucus plug that normally closes and protects the opening to your womb comes away.
If you’d had a baby before, this can happens over a number of days or even weeks before you go into labour but for most first-time mums-to-be, it doesn’t start until you’ve gone into labour.
Once your cervix has effaced, it will start to dilate (or open) from ‘closed’ to 10cm – check out our lovely fruity illustration. When you’re about 3cm dilated, you are officially in the ‘active’ stage of labour. When your cervix has dilated to its full 10cm circumference, you will be ready to push your baby into the world.
The 3 stages of labour: a reminder
- 1st stage: the dilation of the cervix from 0cm to 10cm. This stage is commonly divided into a) early or pre-labour, which involves the effacement of the cervix and then the 1st few centimetres’ dilation and b) active labour, where dilation continues up to 10cm.
- 2nd stage: the pushing stage, from when the cervix is fully dilated until the baby is born
- 3rd stage: the delivery of the placenta.
2. What does cervical dilation feel like?
“Your womb contracts to cause the effacement and then the dilation of your cervix,” says Dr Philippa. “And, as we all know, contractions can hurt while they happen. You may feel this as pressure on your cervix. Or you may feel the pains in your lower back or abdomen.
“Initially, they can be faint and irregular but, as labour progresses, they become regular and more intense.
“Your midwife will probably have advised you to contact your labour ward/delivery centre once your contractions are coming regularly, at least every 5 minutes or so, and lasting at least 1 minute.”
3. How long does it take to dilate to 10cm?
“The first stage of dilation involving effacement and then the gradual dilation up to about 3cm, can take some time – even a few days if you’ve had a baby before,” says Dr Philippa. “But it can also happen much quicker than that. So this first or early stage is very variable – both in length of time and in how much it hurts.
“Once you are at 3 to 4cm and in active labour, the cervix generally dilates at about 1 cm per hour, though again it can be quicker. If things are progressing much slower than this, then your midwife may consider interventions to help.”
4. Is there anything you can do to dilate faster?
“Keeping moving, changing positions, walking about, getting in a warm bath/pool: these can all help speed up contractions,” says Dr Philippa. “There are also medical interventions to speed up dilation, including breaking your waters, where a small hook is inserted through your cervix to break the membranes around the baby.
“Alternatively, or additionally, a drip containing the hormone syntocinon can also be used to stimulate contractions – and it is the contractions that cause the dilation of the cervix. The stronger the contractions, the stronger the effects on the cervix.”
5. If you’re, say, 4cm dilated, how long will it be until you have your baby?
“The general progression is about 1cm per hour,” says Dr Philippa. “But, as we’ve seen, things are variable, especially in the early 1st stage before active labour.
“Once you are at 10cm dilated, you enter the ‘2nd stage’ of labour, which lasts until the baby is born. This is generally lasts about an hour or 2. After an hour or so of pushing, your midwife may consider advising intervention to help with delivery.”
6. Do you to have to dilate to 10cm before your baby comes?
You might think that if you’re baby is measuring small, you may not need to dilate to 10cm to deliver her. Not so.
“You have to be fully effaced and dilated in order to deliver the baby,” says Dr Philippa. “In fact, if you feel the urge to push, your midwife is likely to check – with a vaginal examination – before allowing you to push as, sometimes, the pressure on your rectum (bottom) can make you can feel the urge before full dilation. But pushing against a not fully dilated cervix can cause problems, so your midwife will ask you to hang on!”
About expert GP Dr Philippa Kaye
Philippa Kaye is a GP, author, journalist and mother of 3. She specialises in children’s and women’s health, frequently appears on TV and radio, and is the author of Your Pregnancy Week by Week (Vermilion, 2010).