This is a condition where antibodies in a pregnant woman’s blood destroy her baby’s blood cells. It is also known as Rhesus Disease. HDN does not harm the mother but it can cause the baby to become anaemic and develop jaundice.
HDN only happens when the mother has rhesus negative blood (RhD negative) and the baby in her womb has rhesus positive blood (RhD positive). The mother must have also been previously sensitised to RhD positive blood.
Sensitisation happens when a woman with RhD negative blood is exposed to RhD positive blood, usually during a previous pregnancy with an RhD positive baby. The woman’s body responds to the RhD positive blood by producing antibodies (infection- fighting molecules) that recognise the foreign blood cells and destroy them.
If sensitisation occurs, the next time the woman is exposed to RhD positive blood, her body produces antibodies immediately. If she is pregnant with a RhD positive baby, the antibodies can cross the placenta, causing HDN in the unborn baby. The antibodies can continue attacking the baby’s red blood cells for a few months after birth.
The most common time for a baby’s blood cells to get into the mother’s blood is at the time of birth. But it can happen at other times, for example during a miscarriage or termination of pregnancy, or if something happens during the pregnancy such as having an amniocentesis, chorionic villus sampling, vaginal bleeding or after abdominal injury.
HDN is prevented by giving the mother injections of a medication called anti-D immunoglobulin. All women are offered blood tests as part of their antenatal screening to find out whether their blood is RhD negative or positive. If the mother is RhD negative she will be offered injections of anti-D immunoglobulin at certain points in her pregnancy when she may be exposed to the baby’s red blood cells. This anti-D immunoglobulin helps to remove the RhD foetal blood cells before they cause sensitisation.
If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the Yellow Card Scheme at https://yellowcard.mhra.gov.uk. By reporting side effects you can help provide more information on the safety of these medicines.