Anyone who has ever watched a film or a television programme depicting birth will likely have heard the term “dilated”. That is, a number in centimetres followed by the word dilated. During labour, if you agree to a vaginal examination, you will likely hear that phrase. And it is easy to get distracted by it and focus on the numbers.
Care providers will often tell you that you are not in labour until a magic mark of 4-5cm dilated. If you consent to vaginal examination during labour you will likely hear a number followed by “dilated”.
What is the cervix?
The cervix is the exit, or the “neck” of the uterus. It’s job, during pregnancy is to keep everything in place, and to stop anything getting in.
If you think of it as like a funnel, it is the thinner bit at the bottom.
It is still part of the uterus itself, although it acts differently during pregnancy to make sure that everything stays safe.
At the end of pregnancy, when baby is getting ready to be born, this cervix starts to change, to allow the baby to move down and be born.
“Dilated” is the term for how open the bottom part of the funnel is – baby will be moving down into this bottom section as labour progresses – but it also expands out the way of baby too.
We know that birth happens best when we are relaxed. Perhaps instead of focusing on the numbers, ask them not to share the details – or even don’t consent (the choice is yours!) Although a vaginal examination isn’t just to check how dilated you are. But choice is important!
Your cervix does have an important job during your pregnancy and in birth though. There is so much going on with your cervix when preparing for, and in labour.
Things like baby’s positioning, strength and intensity of contractions and how relaxed the birthing person is also play a really important role in birth. It would be very hard for the uterus and the cervix to do their jobs without everything falling into place and working together.
Firstly, the cervix part of the uterus. It acts a little differently in that it needs to go on a journey before it is ready to dilate, and to birth a baby. But, it really helps to think of the uterus and cervix as part of the same organ.
They need to work together.
You could think of it like a champagne bottle and its cork.
Without the cork the contents of the bottle is open to the air.
Before you can get to the good contents inside, the cork needs to be taken out of the bottle. For birth, the cervix doesn’t get released, nor open, but in fact peels back over baby’s head as they move down and becomes part of the uterus.
This allows a big band of muscle to build at the top of the uterus to help give power to birth baby.
Perhaps the champagne and cork analogy isn’t quite correct but it certainly got your attention!?
What is the cervix like?
During pregnancy, your cervix is like thick cartilage (a bit like the end of your nose), closed and plugged with mucus.
It is about two and a half centimetres long, about the distance between the tip of your finger and your second knuckle.
It also starts off pointing towards the back wall of your vagina.
How does it change?
As your body starts getting ready for labour and birth, it will release hormones called ‘prostaglandins’. These will help it begin to soften, ripen, and do its thing!
As this starts, the mucus plug may also start to come away. Sometimes called a ‘show’, you may notice it in your pants, or when you wipe after going to the toilet. You may also not notice anything, but it will come away at some point.
Then it begins. Your cervix has one heck of a journey to go on and it will start before you even realise you are in labour!
The jobs of your cervix preparing for birth
1. Effacement – how long your cervix is
Effacement is measured in percentages.
We know that the cervix is roughly 2.5cm long during pregnancy. Imagine from your main knuckle on your index finger.
You are about 50% effaced if your cervix only reaches from the tip of the finger to the first knuckle, .
This process must start to happen before dilation can even occur. In many people, it occurs at the same time or it overlaps dilation.
We often see effacement first, then dilation quickly follows. So while you might “still” be 4cm dilated, you may have gone from 50% effaced to 90% effaced!
2. Ripening – softening
Touch the tip of your nose. That’s about the texture of a closed, uneffaced cervix. Imagine birthing a baby through something that hard?
It has to soften, or “ripen” in order to do its other jobs. This primarily starts before labour begins but continues as you progress.
So again, you might “still” be 4cm dilated, but your cervix may have softened from feeling hard to feeling like the inside of your cheek!
To protect your baby, your cervix points towards your tailbone (posterior) during pregnancy and is often too far up for a person to feel during examination.
To open and allow the baby to move through it, your cervix must shift its position until it is pointing directly into your vagina (anterior).
Dilation cannot happen unless the cervix is doing all of its other jobs already. The process often starts before contractions begin. But they often happen seemingly in tandem.
So, someone may be “stuck at 5cm” for a while. But their cervix is effacing, softening, and moving forward and doing all of the other jobs!
“Let me let you in on a secret, your cervix is not a crystal ball. It cannot predict when labour will start. Nor can it predict if you will deliver before, after or even on your due date. The cervix can do many wonderful things, but let’s not give the cervix more credit than it is due. A cervix cannot predict the future.”
It cannot say how long labour will last.
How do the uterus and cervix work together?
Thinking back to the idea that the cervix and uterus are the same organ. They need to work together in tandem.
Often all the focus is on the uterus opening the cervix with contractions. What is happening is that the uterus is moving the baby down, whilst bringing tissue from the cervix up into the uterus.
This will create a strong band of muscle at the top of the uterus to expel baby into the world, instead of that hard tissue keeping baby inside.
Birth expert Carla Hartley says:
“The purpose of labor is NOT the creation of an opening or a hole… The purpose of labor contractions and retractions is to BUILD the fundus, which will, when it is ready, EJECT the baby, like a piston… the cervix does not dilate out….it dilates UP as a result of the effort to pull muscles up into the uterus to push muscles up to the fundus. The cervical dilation is secondary to that. The cervix is pulled up as a result of the building of the fundus.”
So perhaps, instead of thinking how many centimetres there are left to go, you could think how much power is there in the uterus to bring baby out?
How can we give power to these contractions and this uterus?
To help the cervix move out of the way!