Considerations and approaches for early onset fetal anemia due to red cell alloimmunization.

There is no widely accepted definition for early onset hemolytic disease of the fetus and newborn (EOS-HDFN). Several reported series of patients managed with intravascular intrauterine transfusions (IVT's) prior to 20-22 weeks' gestation have been associated with a perinatal mortality of 20 %. It would therefore seem appropriate to define EOS-HDFN as a fetal demise, hydrops fetalis or the need for intrauterine transfusion for suspected fetal anemia prior to 20-22 weeks' gestation. Evaluation of the patient in her next pregnancy with EOS-HDFN history should include a free fetal DNA analysis at 10-12 weeks' gestation to confirm the at-risk fetus. Weekly middle cerebral artery peak systolic velocity determinations using Doppler ultrasound should be initiated by 15 weeks' gestation. Immunomodulation with intravenous immune globulin with or without plasmapheresis should be considered as early at 10-12 weeks' gestation. If IUT's are required prior to 20 weeks' gestation, an intraperitoneal approach can be used until a more advanced gestation can be attained when intravascular fetal access is possible. In the near future, neonatal Fc receptor blockade with a monoclonal antibody may supplant invasive IUT's in the treatment of EOS-HDFN.