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Wirral University Hospital NHS Foundation Trust

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Rhesus Negative

People who are Rhesus positive (Rh pos) have a substance known as 'D antigen' on their red blood cells, whereas Rhesus negative (Rh neg) people do not.

If an Rh neg woman carries an Rh pos baby, there is a slight risk that a small amount of the baby’s blood could enter the mother’s bloodstream.

This could cause an immune response to the D antigen and her body will produce antibodies against it, which stay in her blood forever.

This doesn’t usually affect the existing pregnancy but can cause difficulties in subsequent pregnancies.

The antibodies in the mother’s blood can cross the placenta and attach to the D antigen on the baby’s red blood cells. This can harm the baby and cause anaemia and jaundice. 

Anti-D Immunoglobulin - Wirral Women and Children’s Hospital advises all Rhesus negative women to accept a prophylactic Anti-D injection at certain times:

  • Should there be any bleeding during the pregnancy
  • Following miscarriage and amniocentesis
  • Routinely at 28 weeks gestation
  • Following birth, if the baby is Rhesus positive
  • For further information, visit www.nice.org.uk/TA156.