Haemolytic Disease of the Newborn (HDN)
Mothers and Babies
Sometimes during pregnancy a small amount of the baby’s blood crosses over into the mother’s blood-stream. There are a number of ways by which this can happen including during normal birth, by abdominal injury, Caesarean section, or when an amniocentesis is undertaken.
This is quite usual and causes no harm because the mother’s immune system recognises the baby’s blood as being different from her own and quickly cleans it out of her system.
To do this, the mother’s immune system produces special proteins, called antibodies. These attach themselves to the baby’s red blood cells, which are in her bloodstream and destroy them. This immune response occurs in a similar way when any microbe or foreign body enters the circulation.
From then on, the immune system remembers that it has been in contact with the baby’s red blood cells. So, if the same situation occurs again the mother’s immune system will be ready to act swiftly and eliminate them.
However, when a mother who does not have the RhD Factor (so she is RhD-Negative) is carrying a baby who does have the RhD Factor (so the baby is RhD-Positive), there is a small chance that a problem might arise.
Reasons why baby’s blood can cross over into the mother’s bloodstream:
- amniocentesis*
- chorionic villus sampling*
- injury to the abdomen (such as seat-belt injury)
- vaginal bleeding during pregnancy
- miscarriage
- termination of pregnancy
- child birth
- Caesarean birth
*Procedures sometimes carried out on pregnant women
Please contact your GP or Midwife, for further information about the RhD Factor and what it means to you.
