Your trusty placenta never seems to get much attention in the pregnancy manuals, so, rather belatedly, here's the lowdown...
It looks like a large discus (or a teeny spaceship, if that makes more sense), about 25cm in diameter and a few centimetres thick. At term, the placenta weighs about one-sixth of your baby's weight. If you go to 42 weeks, it can start to get a bit worn, which is why your antenatal team will be trying to encourage your baby to come out if you go too long overdue.
And the placenta even gets its own 15 minutes of fame during the birthing process, too. The ‘third stage’ of labour is delivering the placenta. Once you’ve stopped bellowing like a rutting stag and are holding your baby in your arms, everything else may seem completely insignificant but the organ you grew from scratch and that’s been busy in your uterus, giving your baby oxygen and nutrients and taking out the trash, now gets its brief glimpse of the world outside (before usually being swept unceremoniously into a bin bag and disposed of). Here’s what happens:
Light contractions will help the placenta to break away from the uterine wall and, as it does so, the blood vessels inside the uterus will seal. Depending on your circumstances, you can choose between ‘active’ or ‘physiological’ management of this third stage.
A physiological third stage can take between 15 minutes and an hour, and the umbilical cord will be clamped and cut only once the cord has stopped pulsating or when the placenta has been delivered. It is thought that the last few minutes of receiving blood from the placenta may have benefits to the baby, which is why some prefer no intervention (ie no clamping or cutting of the cord) during this stage.
A very small number of women actually choose not to have the cord cut at all and wrap the placenta and carry it round with the baby until the cord naturally detaches, but most people find this a step too far in the ‘placenta appreciation’ stakes.
Active management is where you are given an oxytocin hormone injection (which you probably won’t even feel) just after the birth. It encourages a few big contractions which expel the placenta and minimise blood loss. The umbilical cord is clamped and cut soon after the birth. The midwife might apply pressure to your abdomen while keeping hold of the umbilical cord, but compared to what you have just been through, this is usually a doddle. Active management is done in the majority of births because it reduces the risk of post-partum haemorrhage. For this reason, it can be seen as the ‘usual approach’, and, unless you request otherwise, you may find that the midwife is waving a needle towards your thigh.There are studies which suggest that active management increases the risk of retained placenta, where the placenta is not completely delivered, and surgery is then required to remove it. This is because the hormones given encourage the cervix to close, leaving a limited time for the placenta to be delivered. In a physiological third stage, there is no rush to deliver the placenta, so the risk of retained placenta may be reduced.