Cervical dilation and effacement: what to expect, what are the stages and what do they feel like?

What is cervical dilation?

Throughout your pregnancy, your cervix is fully closed and sealed with a mucus plug to protect your developing baby. Cervical dilation (often just called dilation) is the process in which your cervix gradually opens so that, during labour, your baby can pass through into your vagina to be born.

Dilation is measured by midwives in centimetre stages – as you can see in our chart above – with 0cm being the completely closed stage and 10cm (the approximate diameter of a baby's head) being the fully dilated stage.

When you're about 3cm dilated, you are officially in the 'active' stage of labour (see The 3 stages of labour, below). When your cervix has dilated to the full 10cm, you will be ready for the final pushing stage of labour that precedes the birth.

What is effacement?

Cervical effacement (often called 'ripening' in the past) is what usually starts to happen before dilation – and it's where your tightly closed cervix stretches, softens and thins, and the mucus plug that's been closing and protecting the opening to your womb comes away.

Midwives and doctors tend to talk about effacement in percentages – with '100% effaced' meaning that your cervix is fully thinned.

Effacement doesn't have to complete before dilation starts; the stages of effacement and dilation tend to overlap, with effacement starting first and completing before dilation is fully complete.

The process of effacement and dilation up to 3cm is called 'pre-labour' or the 'early phase of labour' (see The 3 stages of labour, below). Once your cervix is 100% effaced and 10cm dilated, you will be ready to push your baby into the world.

The 3 stages of labour

• 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.

When does effacement and cervical dilation happen? What are the signs?

Well, to be honest, there's no telling.

The beginnings of effacement and dilation can occur gradually without you even knowing it, over the last weeks or even months of your pregnancy. Or it can happen much more quickly and lead straight into labour.

That said, for most of us – particularly if we haven't had a baby before – it happens between 37 and 42 weeks of pregnancy, when we are 'full term' and ready to go into labour.

You may not notice any signs when effacement and dilation begin but some pregnant women will have what's commonly called a 'show' or a 'bloody show': that's when mucus plug that's dislodged from the opening of your cervix as it starts to efface shows up in your pants as a small blob or trickle of clear, pink or blood-tinged mucus.

What does it feel like? Does it hurt?

To kick off and sustain effacement and dilation, your womb contracts. You may not notice anything at all at first or you may feel a pressure on your cervix or mild pains in your lower back or abdomen.

Initially, contractions can be faint/unnoticeable and irregular but, as labour progresses, they'll become more regular and more intense.

Unhelpfully, it's hard to line up the intensity of contractions with the progress of dilation: some women can be in the early phase of labour and dilate up to 3cm without even being aware of it; others may be very aware of the contractions from the get go.

Whatever it's feeling like, do follow the advice your midwife will have given you and 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.

How long does it take to dilate to 10cm?

It's very variable, particularly in the first stage.

The first stage of dilation-and-effacement and then the subsequent gradual dilation up to about 3cm, can take some time – even a few days or weeks, if you've had a baby before.

But it can also happen much more quickly than that.

Once you are at 3cm to 4cm and in active labour, your cervix is likely to continue dilating at a rate of about 1 cm per hour, though again it can be quicker.

If things are progressing much more slowly than this, or has stopped altogether, then your midwife or medical team may consider interventions to help.

Once you are 10cm dilated, you enter the '2nd stage' of labour (see The 3 stages of labour, above) and this generally lasts about an hour or two. If you've been pushing for more than an hour or so, your midwife may consider advising intervention to help with delivery.

Is there anything you can do to dilate faster?

It can help speed things up if you keep moving: change positions, walk about, get in a warm bath/pool.

There are also medical interventions your midwife may consider 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 (It is the contractions that cause the dilation of the cervix, so the stronger the contractions, the stronger the effects on the cervix.)

Do you to have to dilate to 10cm before your baby comes?

Yes. You might think that if your baby is measuring small, you may not need to dilate to 10cm to deliver them. Not so.

You have to be fully effaced and dilated in order to deliver a baby. In fact, if you feel the urge to push, your midwife is likely to check – with a vaginal examination – that you are fully dilated before allowing you to push as, sometimes, the pressure on your rectum (bottom) can make you can feel the urge before full dilation. Pushing against a cervix that is not fully dilated can cause problems, so your midwife will ask you to hang on!

Pics: Getty. Illustration: Sabrina Sahota

Read more:

• What does it mean when your baby's head is engaged?
• What happens when you lose your mucus plug?
• Do I need to remove my pubic hair before I give birth?