Hemolytic disease of newborn (HDN) refers to an alloimmune hemolytic disorder in fetuses or newborns caused by incompatibility between the blood types of the mother and the fetus, with Rh and ABO incompatibility being the most common causes (referred to as Rh-HDN and ABO-HDN, respectively) (1). The gene discussed is ABO; the disease is fetal erythroblastosis.