It takes three to tango:
the placenta!

Dept. of Obs & Gynae
Clinical School
University of Cambridge

26 Mar 2021

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What is the placenta?

  • An organ attached to the lining of the womb
  • The vital link between the mum and the baby during pregnancy

What does it do?

  • Transfers oxygen and nutrients to the growing baby via the umbilical cord
  • Removes carbon dioxide and waste products from the baby’s blood
  • Shields the baby against most infections
  • Produces hormones which support the pregnancy

How to keep it healthy?

  • Attend antenatal check-ups regularly
  • Avoid smoking, drinking alcohol and using illegal drugs during pregnancy
  • Consult your doctor before taking any medicines or supplements during pregnancy

First trimester (1-12 weeks)

  • The placenta is formed
  • Some cells from the embryo will form the baby’s side of the placenta, by attaching to the wall of the uterus
  • The umbilical cord is formed. It provides a connection between the baby and the placenta
  • On the mother’s side, there is an increased blood flow to certain “blood pools”

First trimester (continued)

  • The baby’s and mother’s blood will actually never mix. They will be separated via blood vessel walls in these “blood pools”
  • The vessel wall will, however, allow small substances, like oxygen and sugar, to pass between the mother to the baby
  • At end of the first trimester, the baby gets a full blood supply from the placenta

Second trimester (13-27 weeks)

  • The baby will now receive essential substances, such as oxygen and nutrition, via the placenta and the umbilical cord
  • Larger substances, like most bacteria, cannot pass from the mother to the baby, which means that the baby is protected from most pathogens even if the mother gets infected
  • Waste products from the baby are transported via the placenta to the mother, and are then processed further in the mother’s organs

Third trimester (28-40+ weeks)

  • Immunoglobulin G antibodies can pass from the mother to the baby. These antibodies can help the baby’s immune system to recognise and destroy pathogens
  • At end of pregnancy, the placenta weighs around 500 g (or 1lb)

Delivery

  • The placenta detaches from the uterus and is delivered after the baby is born
  • The placenta is usually disposed afterwards. However, sometimes placentas are collected for research purposes
  • The examination of the placenta can help researchers to better understand placental function and the role the placenta plays in a healthy pregnancy, and to develop new tests and therapies to prevent any placenta-related problems in pregnancy

References

Quiz

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