Rh disease is a serious pregnancy problem that can affect a baby (fetus) with Rh-positive blood if the mother has Rh-negative blood. Because their blood types don't match, the mother's immune system will make antibodies that cause the fetus's red blood cells to be destroyed. This can lead to anemia, jaundice, and dangerous swelling.

Rh disease is also called hemolytic disease of the newborn or erythroblastosis fetalis.

Rh disease is the result of Rh sensitization, which causes the Rh-negative mother to make antibodies that attack the fetus's Rh-positive red blood cells. The more red blood cells are destroyed, the worse the effect on the fetus. In severe cases, the baby may die before or after birth.

Rh sensitization usually happens during childbirth, so a fetus in a first pregnancy may not have Rh disease. But each future Rh-positive fetus will be at risk, and Rh disease tends to be worse with each Rh-positive pregnancy.

In some cases, a fetus in a first pregnancy does have Rh disease. This can happen if the mother was Rh sensitized during a miscarriage, abortion, or ectopic pregnancy or because of a test that causes bleeding in the uterus during pregnancy, such as an amniocentesis or chorionic villus sampling. A blood test can show if a woman has Rh sensitization and whether her baby is at risk.

Treatment for Rh disease depends on how severe the disease is, which can be checked with regular testing throughout the pregnancy. A fetus with mild Rh disease may not need any special treatment. One who is more severely affected may need to have a blood transfusion while still in the uterus and to be delivered early.

A woman with Rh sensitization is likely to be cared for by a high-risk pregnancy specialist (perinatologist).