Severe intrauterine hemolysis due to anti-C(w).

C(w) is a low-frequency antigen in the Rhesus blood group system. Anti-C(w) can occur naturally or develop as a result of red blood cell sensitization through transfusion or pregnancy. Clinically significant hemolytic disease of the newborn is rarely associated with anti-C(w), with no previous reported cases of hydrops fetalis or severe fetal anemia resulting in intrauterine death. We report an unusually severe case of intrauterine hemolysis resulting from this rare condition. The neonate presented with early-onset hyperbilirubinemia and severe anemia at birth requiring multiple exchange transfusions in the first 24 hours of life. The mother of this infant had a significantly poor obstetric history, having delivered a stillbirth with massive hepatosplenomegaly previously. This case report suggests that intrauterine hemolysis due to anti-C(w) may be life threatening to the unborn fetus.