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 allows the placenta to carry out functions that your unborn baby can't perform for itself.
The placenta is connected 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 grow and develop. The placenta also gives some protection against infection for your baby while it's in the womb, protecting it against most bacteria. However, it doesn't protect your baby against viruses.
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, more contractions will push the placenta out through the vagina.
Your midwife will offer you a medicine to stimulate your contractions and help push the placenta out. They'll inject the medicine into your thigh just as the baby is born. It makes your womb contract so the placenta comes away from the wall of your womb. This also helps prevent the heavy bleeding 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 check the placenta and membranes, to make sure that they're complete and nothing has been left behind.
If you have a caesarean section, after your baby is born, 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're pregnant. You can also call NHS 111.
Further information:
Your health, your choices