What is the placenta and why is this so important?

5 things to know about the placenta.

1. The placenta is the organ that keeps the baby alive during pregnancy.
2. It is also known as the afterbirth.
3. The placenta performs the function of many organs during pregnancy, including the lungs, gut and kidneys. 
4. If the placenta does not form properly, it can lead to complications such as pre-eclampsia and a baby who does not grow enough, a condition called growth restriction.
5. There are ways to try to predict how well the placenta has developed using blood tests or scans.

What is the placenta?

The placenta is sometimes called the afterbirth. This is the organ that provides the vital link between you and your baby during the pregnancy. It develops from the earliest stages of pregnancy and provides the baby with all of the nutrients the baby needs to grow and develop. It also is the route by which the baby gets rid of things it doesn’t need. In many ways, the organ plays the role of the lungs, the kidney, the gut all in one. It is an amazing thing

The placenta starts to develop really early on in pregnancy, from the moment of conception. The most important stages of development, are, like the other organs, in the early stages of the pregnancy. Most placental development occurs in the first half of pregnancy.

Why is it important?

How well the placenta develops is vital to whether complications of pregnancy, such as high blood pressure (known as pre-eclampsia) and poor growth of the baby, occur. This is because the placenta determines how well nutrients, including oxygen and glucose, transfer to the baby and allow it to grow well. If the placenta does not form very well, then all through the pregnancy, the baby may not get enough nutrients to grow as it should. If this happen, we describe the baby as being growth restricted. It is possible to get an idea how well the placenta has formed by scanning and measuring the blood flows in the big arteries that flow from mum to the placenta. This is measured in women who are at higher risk of placental complications, in the UK it is not offered to everyone. If the blood flow pattern is abnormal, it is more likely that the placenta has not formed as well as it should and there is a higher risk of pregnancy complications. It is also possible to get a clue about placenta development from the levels of the hormones that are measured as part of the Down’s syndrome screening tests. 

In pre-eclampsia it is thought that substances released by the placenta result in the mother’s blood pressure increasing. When there is pre-eclampsia, the most common association is with a baby who is too small, but it can also occur with a baby who is normal size, or even bigger than normal.

Placentas that have not developed very well can also be more likely to separate early, which can cause bleeding. This is a condition called a placental abruption. As the placenta is vital for sustaining life of the baby, if it separates early then this can be very serious, resulting in the need to deliver the baby urgently.

How can I monitor my placenta?

The placenta can be seen on ultrasound scans, and the place it lies within the womb can be seen on the scan. Occasionally, the placenta is found to be lying lower down in the womb, something called a low-lying placenta or the medical term is placenta previa. In the worst cases, this can block the birth canal, meaning that the only option is to deliver the baby by caesarean section, as the way out is blocked by the placenta. A low lying placenta can cause bleeding.

Why is the placenta also called ‘the afterbirth’?

The placenta will deliver after the baby, at the end of pregnancy. Delivery of the placenta is called the ‘third stage’. After the placenta has delivered, it leaves a large raw surface inside the womb where the placenta used to be attached. This is what causes the bleeding after birth. It is important for the womb to contract down and shrink quickly to control this blood loss. If you want, you can see the placenta after the baby is born. It can also be used to collect stem cells and blood after birth and this is something that you might have heard of via the Anthony Nolan Trust. It may not look like much after birth but the placenta is an amazing organ!