Why we need less focus on our cervix and more on our uterus muscles.
Your cervix is attached to your uterus. It has a small opening- one which allows your menstration to pass through, and allows sperm through, but during pregnancy, it actually develops a seal. This seal is commonly known as a mucous plug (gah! Who named our lady parts with such contempt?!).
I actually prefer to call in a uterine seal- as that’s what its function is, but there is also a very powerful relationship between our thoughts and emotions, and when parts of our body, or parts of labour and birth are named in such a way, that we usually think it is dirty, unhygienic etc. it certainly doesn’t help us conjure up those feel good emotions that are useful during birth.
The cervix itself is about 4cm long- but this can depend on our genetic make up, and of course if pregnant and in labour. There will be a time in the lead up to birthing day when it will soften and eventually thin out to open to 10cm (you may or not be aware of labour starting). When you’ve reached 10cm open, this is usually termed “fully dilated”, and is in preparation for baby’s descent and birth. It’s not at all evidence based to subscribe to vaginal exams- which check on cervical dilation- as we know women can thin and open (dilate) fast, some slow, some rest and then open quickly. It’s not a measure of how long your labour is going to last, or how long away baby is to be born.
I have no idea why there is so much focus on the cervix during traditional antenatal education. When you have a contraction (I prefer to call it a surge), what you’re actually feeling is your uterine muscles working together, which opens the cervix, and then once you’re fully open, transitions to then nudging baby down. Now that’s something they should be talking about in childbirth classes! How amazing are those uterus muscles?!?
There are 3 layers to the uterus responsible for your surges. The outer layer is made of longitudinal smooth muscles, the middle layer made of criss-crossing (likened to a figure of 8), and the inner fibers are circular, and attached to your cervix. The middle layer act as living ligature, also commonly known as physiologic sutures (as they tie off blood vessels after birthing the placenta), and help in the prevention of blood loss.
The outer uterus muscles, which are smooth, are the layer responsible for initiating contractions or surges. They have a resting phase, then a contraction phase of varying frequency, duration and intensity. When they contract and shorten at the top, they pull on the inner circular muscles, and hence thin and open the cervix attached at the bottom.
After baby and placenta are birthed, the middle layer of criss-crossed compresses the blood vessel, helping control bleeding after birth. The outer muscles also will continue to contract in order to shrink your uterus, now that baby is earthside.
It's an important part of birth education, to understand the biology and physiology of our amazing body. The pressure and intensity felt as our uterus is in surge needs to be understood, as it's certainly nothing to be feared, nor should it be overlooked.