Hydrops fetalis due to ABO incompatibility.

Hemolytic disease of the newborn due to ABO incompatibility was first observed by Halbrecht in 1944. This entity has a spectrum ranging from minimal hemolysis requiring no therapy, as is the case in most instances, to severe hemolytic disease requiring aggressive management including exchange transfusion in a small percentage of cases. An extreme degree of hemolytic disease of the newborn due to ABO incompatibility, i.e., hydrops fetalis, has not been well documented in the English literature. We present a case of hydrops fetalis due to ABO incompatibility. The severity of hemolytic disease due to ABO incompatibility can be forecast when indicated in selected cases.