What is the placenta?

The placenta is an organ attached to the lining of your womb during pregnancy.

It keeps your unborn baby’s blood supply separate from your own blood supply, as well as providing a link between the two. The link enables the placenta to carry out functions that your unborn baby can’t perform for itself.

The placenta is linked to your baby by the umbilical cord. Your baby is inside a bag of fluid called the amniotic sac, which is made of membranes.

What does the placenta do?

Oxygen and nutrients pass from your blood supply into the placenta. From there, the umbilical cord carries the oxygen and nutrients to your unborn baby. Waste products from the baby, such as carbon dioxide, pass back along the umbilical cord to the placenta and then into your bloodstream, for your body to dispose of them.

The placenta produces hormones that help your baby to grow and develop.

The placenta also gives some protection against infection for your baby while it's in the womb. It protects your baby against most bacteria. However, it does not protect your baby against viruses. For example, if you’re not immune to the rubella virus (German measles), it can cross the placenta and cause miscarriage, stillbirth or birth defects such as deafness, brain damage, heart defects and cataracts.

Alcohol, nicotine and other drugs can also cross the placenta and can cause damage to your unborn baby.

Towards the end of your pregnancy, the placenta passes antibodies from you to your baby, giving them immunity for about three months after birth. However, it only passes on antibodies that you already have.

What happens after my baby is born?

After your baby is born, in the third stage of labour, more contractions will push the placenta out through the vagina. At this stage, the placenta is also called the afterbirth.

Your midwife will offer you an oxytocic medicine to stimulate your contractions and help push the placenta out. They will inject the medicine into your thigh just as the baby is born. It makes your womb contract so that the placenta comes away from the wall of your womb. This also helps prevent the heavy bleeding that some women experience.

Breastfeeding your baby as soon as possible after the birth helps your womb to contract and push the placenta out.

Read more about breastfeeding your baby during the first few days.

You may choose to let your body push the placenta out in its own time, which may involve some loss of blood. 

After the birth, your midwife will inspect the placenta and membranes, to make sure that they are complete and nothing has been left behind.

If you have a caesarean section, after your baby has been lifted from your womb, the placenta will also be delivered.

Always speak to your midwife or GP if you are concerned about any aspect of your health when you are pregnant. You can also call NHS 111.

Read the answers to more questions about pregnancy. 

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Page last reviewed: 29/11/2013

Next review due: 28/11/2015