Dilation: what each centimetre means in labour
In this article
Dilation is how far your cervix, the neck of the womb, has opened, measured in centimetres from closed to 10cm. HealthHub describes the first stage of labour as the cervix opening up to 10cm. At 10cm you are fully dilated and the pushing stage begins. Your doctor or midwife checks dilation with a vaginal examination, usually every few hours in labour.
| Measured in | Centimetres, from closed to 10cm |
|---|---|
| Early (latent) phase | Up to about 3 to 4cm; can take many hours |
| Active labour | From about 4cm, roughly 1cm an hour, KKH says |
| Fully dilated | 10cm, when the pushing stage starts |
| Checks at SGH | A review about every 4 hours |
How dilation is checked
The only way to know how dilated you are is an internal (vaginal) examination by a doctor or midwife. SGH says the team or your obstetrician reviews you about every 4 hours in the delivery suite, with a vaginal examination to check progress. KKH doctors, writing on HealthXchange, say the checks become more frequent later on and can be quite uncomfortable.
The same examination also tells the midwife how soft and thin your cervix is, which is called effacement. The NHS says you can decline the checks, and the midwife should explain why they are being offered.
How fast the cervix opens
The first part is slow. HealthHub says that in the latent phase the cervix opens to about 3cm, this can take many hours, and the contractions are usually not so painful. The NHS puts the start of established labour at about 4cm.
After that, things move faster. KKH says that once you pass 4cm you open about 1cm an hour, which works out to around 6 more hours to reach 10cm. It also says the time frame is only a guide, and some mothers go much faster. The NHS gives a wider range: usually 8 to 18 hours from established labour to full dilation in a first pregnancy, and around 5 to 12 hours in a second or third.
When dilation slows down
Slow progress is one of the main reasons labour plans change. In a KKH FAQ on SingHealth, the doctors say there is about a 10% chance of an emergency C-section, and failure to progress in cervical dilation and in the baby's head moving down is one of the reasons. They also say it is often hard to predict before labour starts.
Before that point, the team has other options. The NHS describes breaking your waters to make contractions stronger and more regular, then an oxytocin drip if that does not work. KKH says it may prescribe an oxytocin infusion to regulate your contractions if labour is not progressing well.
What full dilation means for you
At 10cm the second stage of labour begins and ends with the birth of your baby. HealthHub says contractions become more intense and you feel an urge to push, a bit like needing to open your bowels. It says this stage can last 1 to 1.5 hours for a first-time mother, or just minutes for women who have given birth before.
SGH describes a passive phase at full dilation, usually one to two hours, when involuntary contractions move the baby down before active pushing begins. Our guide to the stages of labour follows each stage in order.
Frequently asked questions
Can I be dilated before labour starts?
Yes. Cleveland Clinic says some women stay 2cm dilated and partly effaced for weeks, while others stay closed until a few days before delivery. Being a little dilated does not mean labour is starting today.
How long does it take to go from 4cm to 10cm?
KKH's rough guide is about 1cm an hour, so around 6 hours. The NHS says 8 to 18 hours is usual in a first pregnancy and 5 to 12 hours in later ones.
Does a cervical check hurt?
It can be quite uncomfortable, KKH says, especially during strong contractions. Tell the midwife if you need her to stop or wait for a contraction to pass.
Is dilation the same as effacement?
No. Dilation is the cervix opening, measured in centimetres. Effacement is the cervix thinning, given as a percentage. Both need to be complete before you push.
Related terms
- Effacement: The thinning and shortening of your cervix before and during labour, given as a percentage from 0 to 100.
- Contractions: The tightening and relaxing of your womb that opens the cervix and pushes your baby down in labour.
- Induction of Labour: Starting labour with medical help, such as a pessary, balloon or drip, instead of waiting for it to begin.
- Epidural: Labour pain relief given through a fine tube in your lower back by an anaesthetist, numbing the womb and birth canal.
- Rupture of Membranes (Water Breaking): When the bag of fluid around your baby breaks and leaks out through the vagina, as a gush or a trickle.
- HealthHub - Labour and Delivery: What to Expect (read 9 November 2026)
- KKH via HealthXchange - Pregnancy Week 34: Preparing for 3 Stages of Labour (read 9 November 2026)
- SGH - Going into Labour (read 9 November 2026)
- SingHealth (KKH) - Pregnancy Labour and Delivery (read 9 November 2026)
- KKH - Labour and delivery (read 9 November 2026)
- NHS - The stages of labour and birth (read 9 November 2026)
- Cleveland Clinic - Cervical Effacement (read 9 November 2026)
