Definition of Erythroblastosis fetalis:

Erythroblastosis fetalis is a potentially life-threatening blood disorder in a fetus or newborn infant. This article provides a general overview. For more detailed information see the specific disorder:

• ABO incompatibility
• Rh incompatibility

Causes, incidence, and risk factors:

Erythroblastosis fetalis develops in an unborn infant when the mom and the baby have different blood types. The mother produces substances called antibodies that attack the developing baby's red blood cells.

The most common form of erythroblastosis fetalis is ABO incompatibility, which can vary in its severity.

The less common form is called Rh incompatibility, which more often causes a very severe anemia in the baby.