What Every Woman Should Know about Pregnancy and the Uterus


Long before my love of all things yoga, pregnancy and lycra there was my love of hard science. And – albeit in a veterinary sense – reproduction was kinda my thing! I even taught it at Cambridge. (Yep, actual Cambridge, the one with dreaming spires, Pimms o’clock and really hard exams. Hard to believe when I’m in my unicorn leggings, I know…).

My nerd-ish tendencies have had a few consequences:

a) If you’ve ever wondered what species boasts a corkscrew-shaped penis, full-pint ejaculation and the 30-minute female orgasm, I’m your girl!

b) I’m really passionate about applying science to making pregnancy and birth safer and easier.

So, with that in mind, here’s today’s science bit A.K.A. what’s actually happening to your uterus in labour, simplified.

Yoga and the Uterus

We can think of the uterus as a muscular bag designed to hold a baby during pregnancy. The muscles it’s composed of are involuntary. Just like the muscles that give us goosebumps or make our heart beat, we can’t consciously control them. We can, however, influence their action with the bodily environment we create – and that’s where yoga comes in.

The uterine muscles (myometrium) sit in two main layers. One runs vertically up and over the top of the uterus (the end which finishes near the rib cage at full term) and one runs horizontally, forming bands or loops encircling baby and the placenta as they grow.

During pregnancy, the upper vertical muscles remain relaxed while the tone in the strong horizontal muscles – especially those at the bottom of the uterus close to the cervix – hold baby up and in, exactly where we want them to be.

During labour, their roles reverse. Working as a pair, much like your biceps and triceps, their action draws baby down the abdomen and out of the uterus into the birth canal.

pregnancy yoga prenatal uterus muscles myometrium hypnobirthing relaxation

When a woman is calm and relaxed these muscles work in easy harmony.

During a contraction (rush or surge) the upper vertical fibres actively contract and shorten. This draws the inner layer of horizontal muscle fibres – thickest just above the cervix, baby’s way out of the uterus – up and back. This action causes the cervix thin and dilate (open) – eventually reaching that ‘magic number’ of 10cm.

We can often see this action on the outside as Mum’s tummy gets hard or tight, appearing to lift upwards during each rush.
pregnancy yoga prenatal uterus muscles myometrium hypnobirthing relaxation

Unfortunately, when a woman is nervous or tense, this team can’t work quite so harmoniously. From an evolutionary point of view, it’s just not sensible for your body to deliver a baby quickly and in its immediate environment if it senses stress hormones. Unable to differentiate from genuine or perceived threats, our bodies err on the side of caution.

In this case, the horizontal muscles also tense up so are unable to move upwards as the vertical muscles pull on them. It’s a bit like trying to straighten your arm with both your biceps and triceps muscles contracted. The tension from these now opposing muscles combined with the pressure of the baby’s head pressing down onto a cervix that isn’t easily able to open or thin causes pain. When a woman feels this pain, it confirms her worst fears about the impending agony of labour are true. This only heightens the state of stress that initially caused the problem. This leads to a circle of feedback:

More stress hormones = more opposing muscular action = a longer, more painful labour.

Not so great.

Thankfully, the mindfulness and breathing techniques we learn in yoga teach us to go with each wave or surge, instead of resisting it. Even if the strong sensations of a rush do start to cause panic, we’re less likely to be overcome by it as we’ve taken the time to really understand that each rush – like everything else in life –  is transitory, We trust our body’s ability to birth our baby and know that each surge brings us closer to meeting our long-awaited baby.

As always, I’m more than happy to answer your questions – just comment below!

If you’re interested in giving pregnancy yoga a try, there’s a new 6-week course starting on the 3rd of June and enrolment is now open! This will be the last course until (at least!) November 2016, so feel free to join us whatever stage of pregnancy you’re at. Find out more here, or to register fill in the form below or send me a message on Facebook.

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