So the uterus is a muscle designed to be a baby’s home during pregnancy. The muscles that make up the uterus are involuntary. Just like the muscles that give us goosebumps or make our heart beat, we don’t have conscious control them over them. We can, however, influence their action and our reaction with the bodily environment we create – and this is where breathing and relaxation can help.
The uterine muscles sit in two main layers. One set runs vertically up and over the top of the uterus (the end which finishes near the rib cage at full term) this is the outer layer and one runs horizontally, forming bands or loops encircling baby and the placenta as they grow this is the inner layer.
During pregnancy, the vertical muscles remain relaxed while the tone in the strong horizontal muscles particularly those at the bottom of the uterus close to the cervix – hold baby up and in.
However 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 and out through the vagina and into the world.
During a contraction (wave 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, move upwards and open.
When a woman is calm, breathing deeply and relaxed these muscles work together, smoothly and in perfect harmony. Unfortunately though when a woman is nervous, anxious or feels tense, this set of muscles can’t work quite so smoothly. You see from an evolutionary point of view, it’s just not sensible for your body to want to birth a baby quickly, into the immediate environment if it senses stress hormones (Adrenalin). Unable to differentiate from genuine or just perceived threats, our bodies err on the side of caution.
In this case, the horizontal muscles also tense up and so find it harder 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 moving down onto a cervix that isn’t easily able to open or thin causes discomfort. When a woman feels this discomfort, it confirms her worst fears about labour and birth. This then 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.
Thankfully, the mindfulness and breathing techniques you can learn in Nurtured Pregnancy Yoga classes teach you how to breath and move with each wave or surge, instead of resisting it. You also learn how to trust in your body’s ability to birth your baby and know that each wave brings you closer to meeting your baby.
Image of the uterus by Student Midwife Studygram