Hemolytic disease of the newborn (HDN) is a serious medical condition that occurs when the blood type of the mother and the fetus are mismatched, triggering an immune response in the mother which results in the destruction of fetal red blood cells. This condition may also be known as erythroblastosis fetalis, neonatal jaundice, or Rh disease. Other synonyms for HDN include Rhesus incompatibility, blood group incompatibility, fetal anemia, and isoimmune hemolytic anemia. Symptoms of HDN may include jaundice, an enlarged liver and spleen, and anemia. Treatment options for HDN include blood transfusions, phototherapy, and immunoglobulin therapy. Early diagnosis and treatment can help improve the prognosis for infants with HDN.