Hemolytic disease of the newborn (HDN) is a blood disorder in a fetus or newborn infant. In some infants, it can be life threatening.

This article provides a general overview. For more detailed information see the specific disorder:

• ABO incompatibility
• Rh incompatibility

HDN; Erythroblastosis fetalis

HDN may develop when a mother and her unborn baby have different blood types (called "incompatibility"). The mother produces substances called antibodies that attack the developing baby's red blood cells.

The most common form of HDN is ABO incompatibility, which is usually not very severe. Other, less common types may cause more severe problems.

The least common form is Rh incompatibility, which can almost always be prevented. When this form does occur, it can cause very severe anemia in the baby.

HDN can destroy the newborn baby's blood cells very quickly, which can cause symptoms such as:

• Edema (swelling under the surface of the skin)
• Newborn jaundice

Signs of HDN include:

• Anemia or low blood count
• Enlarged liver or spleen
• Hydrops (fluid throughout the body's tissues, including in the spaces containing the lungs, heart, and abdominal organs)--which can lead to heart failure from too much fluid

Which tests are done depends on the type of blood group incompatibility and the severity of symptoms, but may include:

• Complete blood count and immature red blood cell (reticulocyte) count
• Bilirubin level
• Blood typing

After birth, a transfusion may need to be performed.

Infants with mild HDN may be treated with:

• Drugs used to treat allergic reactions (antihistamines)
• Drugs used to treat swelling and allergies (steroids)
• Feeding and fluids (hydration)
• Fluids given through a vein (intravenously)
• Light therapy using bilirubin lights
• Medicines to raise blood pressure if it drops too low

The severity of this condition can vary. Some babies have no symptoms. In other cases, problems such as hydrops can cause the baby to die before, or shortly after birth. Severe HDN may be treated before birth by intrauterine transfusion.

The most severe form of this disease, which is caused by Rh incompatibility, can be prevented if the mother takes a medicine called RhoGAM at certain times during and after her pregnancy. If you have had a baby with this disease, talk with your doctor if you plan to have another baby.

Gruslin AM, Moore TR. Erythroblastosis fetalis. In: Martin R, Fanaroff A, Walsh M, eds. Neonatal-Perinatal Medicine. 9th ed. Philadelphia, Pa: Mosby Elsevier; 2011.

Cohen DW. Hemolytic disease of the newborn: RBC alloantibodies in pregnancy and associated serologic issues. UpToDate, Waltham, MA. Nov 2009.