The placenta is the organ that the body grows in pregnancy in order to supply the baby(ies) with the necessary nutrients, oxygen and removal of waste products throughout pregnancy. It is attached to the lining of the womb and will usually embed at the top or side of the uterus, away from the cervix. The placenta provides protection to your baby by passing antibodies that you have developed to help with their immunity for the first few months after birth. Your blood and your baby’s blood do not actually mix during pregnancy, the placenta prevents this from happening. Think of it as a barrier that communicates between the mother and baby. Or if you are wanting the sciencey stuff: it is an exchange surface that nutrients and gases cross by diffusion.
The placenta does its best to protect the baby, but it cannot prevent all harmful substances from crossing the barrier such as alcohol, drugs and certain prescribed medications. Infectious diseases can also cross over.
So to put it all in context, the placenta is attached to the uterus and the amniotic sac is attached to the placenta.The amniotic sac is made up of two membranes which contain the baby, the cord and amniotic fluid inside. The umbilical cord connects the placenta to your baby. Blood vessels run through the cord delivering the nutrients to the baby and removing the waste products. The first two pictures below show the side of the placenta that the baby is in contact with.
When the baby is born, the cord will usually be clamped and cut to separate the baby from the placenta. Research has shown that delayed cord clamping – where the baby stays attached to the placenta until the cord has stopped pulsating or the placenta is delivered -is extremely beneficial for the baby. This is because when the baby is born one third of their blood is contained in the cord and placenta, so if the cord is cut immediately they will not receive their full blood volume.
There are two ways for the placenta to be delivered:
- Nature’s Way (physiological management) – After the birth of the baby there is a huge peak of oxytocin, the hormone that acts on the uterus causing it to contract. This causes the placenta to detach from the wall of the uterus and then the placenta can be pushed out with your effort. It does not feel the same as pushing out your baby as it is soft and squishy. Sometimes, if the placenta has detached already it is simple enough as just moving to a more upright position and it slides out easily. Having skin-to-skin with your baby during this time and helping them to breastfeed for the first time aids the flow of oxytocin (the love hormone) too, which further helps the uterus do it’s job of expelling the placenta.
- ‘Active Management’ – This involves giving a drug containing oxytocin by injection into your leg soon after the baby is born. It causes a big contraction which acts in the same way to expel the placenta. The midwife will then help to deliver the placenta by pulling on the umbilical cord and may ask you to push at the same time. Active management is generally recommended if there is added risk of you bleeding more than is normal after birth. For example, if the birth has been complicated or there have been other interventions.
I hope you’ll agree that the placenta is a truly fascinating part of pregnancy. I have tried to focus on the basics here, and haven’t delved into some of the abnormal things that placentas can get up to… that’s for another time I think!