AbstractObjectiveTo determine perinatal outcome in pregnancies with early severe red blood cell (RBC) alloimmunization.MethodsThis was a retrospective analysis of 30 patients requiring their first intrauterine transfusion (IUT) at < 22 weeks of gestation. Timing of the first IUT was based on evaluation of either the middle cerebral artery peak systolic velocity (MCA‐PSV) or development of ascites.ResultsThirty‐three per cent of the patients had experienced a previous intrauterine fetal death as a result of RBC alloimmunization. Of these alloimmunized pregnancies, 26 (87%) were associated with anti‐D, four (13%) with anti‐Kell and 12 had more than one antibody type involved. The antibody titers before the first IUT ranged from 1:128 to 1:8024. All fetuses were severely anemic before the first IUT with a median hemoglobin (Hb) level of 37 (range, 3–81) g/L. The nine hydropic fetuses had a lower Hb level compared with non‐hydropic fetuses (median 15 g/L vs. 42 g/L, P = 0.016). However, 15 (71%) non‐hydropic fetuses had an Hb level of < 50 g/L before the first IUT. The median gestational age at the first IUT was 20.4 (range, 16–22) weeks, and between one and nine transfusions were needed during pregnancy. Transfusion was via the intrahepatic vein (IHV) (n = 19), umbilical vein (n = 6) or umbilical artery (n = 2), or was intracardiac (n = 2) or intraperitoneal (n = 1). Overall perinatal survival rate was 80% and did not differ between hydropic and non‐hydropic fetuses. Median gestation at delivery, after exclusion of six intrauterine fetal deaths, was 36.7 (range, 27.8–38.4) weeks.ConclusionsIn early severe RBC alloimmunization, fetuses can be severely anemic without hydrops, and prognosis cannot be predicted by the presence or absence of hydrops. Early IUT followed by serial transfusions is associated with a perinatal survival rate of about 80%. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.