Hemolytic disease due to fetomaternal alloimmunization

Hemolytic disease due to fetomaternal alloimmunization, also known as hemolytic disease of the fetus and newborn (HDFN) or erythroblastosis fetalis, is a condition in which maternal antibodies cross the placenta and attack fetal red blood cells, leading to their destruction (hemolysis). This occurs when there is an incompatibility between maternal and fetal blood group antigens — most commonly involving the Rhesus D (RhD) antigen, but also other Rh antigens (c, C, E, e) or non-Rh systems such as Kell, Duffy, or Kidd. During pregnancy or delivery, fetal red blood cells may enter the maternal circulation, triggering the mother's immune system to produce IgG antibodies against the foreign antigen. In subsequent pregnancies with an antigen-positive fetus, these antibodies cross the placenta and cause fetal red blood cell destruction. The disease primarily affects the hematologic system of the fetus and newborn, but can have widespread consequences. Key clinical features include fetal anemia, which in severe cases can lead to hydrops fetalis (generalized edema, pleural and pericardial effusions, and ascites), hepatosplenomegaly, and even fetal death. After birth, affected neonates may develop severe jaundice due to unconjugated hyperbilirubinemia, which if untreated can cause kernicterus (bilirubin-induced brain damage). Reticulocytosis and the presence of nucleated red blood cells (erythroblasts) in the peripheral blood are characteristic laboratory findings. Treatment depends on severity and timing. Prenatal management includes close monitoring with Doppler ultrasound of the middle cerebral artery to detect fetal anemia, and intrauterine transfusion in severe cases. Postnatal treatment includes phototherapy and exchange transfusion to manage hyperbilirubinemia, as well as supportive care for anemia. Prevention of RhD alloimmunization is achieved through administration of anti-D immunoglobulin (Rh immune globulin) to RhD-negative mothers during pregnancy and after delivery. This prophylactic measure has dramatically reduced the incidence of RhD-related HDFN, though cases due to other blood group antigens remain an ongoing clinical challenge.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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