Anti D

What is Anti D?

Anti D is the common term for Rh (D) immunoglobulin. It’s an injection of a special antibody collected from blood donors.

What are blood groups and how do we get ours?

Every person has a blood group or “type.” Your blood type is determined by proteins that attach to your red blood cells. You inherited your blood type from both parents. A baby can have a different blood type to its mother. Occasionally, this difference can lead to problems.

Explain the Rh blood types

Rh blood type depends on whether or not you have the Rh protein attached to your red blood cells.

  • Around 85% of people have this protein – their blood type is Rh positive.
  • Around 15% of people do not have this protein – they are Rh negative.

Why are Rhesus blood types important in pregnancy?

During pregnancy, a small amount of the baby’s red blood cells can flow across the placenta into the mother’s blood. This can happen silently, without the mother even realizing anything has happened.

Remember that the baby can have a different blood type to the mother. If the baby is Rh positive, but the mother is Rh negative, the mother’s immune system can react against the fetal red blood cells by producing antibodies.

The antibodies usually aren’t a problem for the first pregnancy. However, antibodies stay in the mother’s blood for years. If she goes on to have another Rh positive baby, her antibodies can cross the placenta and attack the fetal red blood cells. This can cause serious problems for the baby, including severe anaemia, brain damage and stillbirth.

How does Anti D prevent these complications?

When Rh positive blood cells flow across the placenta, there is a window of time before a Rh negative mother starts to produce antibodies. If we inject Anti-D into the mother during that window, the Anti-D will “mop up” the fetal red blood cells. This prevents the mother’s immune system from making antibodies.

When is Anti D given?

Anti D is given to Rh negative women at the following times:

  • At around 28 and 34 weeks of pregnancy
  • When there is an increased risk of fetal red blood cells entering the mother’s blood stream (e.g. miscarriage, amniocentesis)
  • After birth of a Rhesus positive baby

As always, this information is intended for general educational purposes only. It is not medical advice. Please discuss any medical issues with your own doctor. Read our full medical disclaimer here.