Rhesus disease
Overview
Rhesus disease is a condition where antibodies in a pregnant woman's blood destroy her baby's blood cells. It's also known as haemolytic disease of the foetus and newborn (HDFN).
Causes
Rhesus disease 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's pregnant with an RhD positive baby, the antibodies can cross the placenta, causing rhesus disease in the unborn baby. The antibodies can continue attacking the baby's red blood cells for a few months after birth. Read more about thecauses of rhesus disease.
Prevention
Rhesus disease is uncommon these days because it can usually be prevented using injections of a medication called anti-D immunoglobulin. All women are offeredblood testsas part of theirantenatal checks and teststo determine whether their blood is RhD negative or positive. If the mother is RhD negative, she'll 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 can cause sensitisation. If a woman has developed anti-D antibodies in a previous pregnancy (she's already sensitised) then these immunoglobulin injections don't help. The pregnancy will be monitored more closely than usual, as will the baby after delivery. Read more aboutpreventing rhesus diseaseanddiagnosing rhesus disease.