Alloimmunization in Pregnancy: Implications for the Fetus and Neonate

Blood group or red cell alloimmunization occurs when a pregnant patient has produced antibodies to a blood group antigen possessed by the fetus and not possessed by the pregnant patient. Maternal antibodies are usually produced as an immune response to fetal-maternal bleeding or blood product transfusion. Prevention remains the most important strategy to avoid the formation of maternal antibodies or alloimmunization. Maternal alloimmunization may result in transplacental passage of these antibodies into the fetal circulation and the potential for fetal or neonatal hemolysis and anemia. Red cell alloimmunization can result in significant perinatal morbidity and mortality. Management of alloimmunization in pregnant patients should be protocol-driven. Current strategies for assessment and therapies allow for more thorough and less invasive management with risks to mother and fetus.