Rhesus disease is uncommon these days because it can usually be prevented using injections of a medication called anti-D immunoglobulin.
All women are offered blood tests as part of their antenatal checks and tests to 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.