['This study was undertaken to test the hypothesis that the degree of immune fetal hydrops predicts outcome in red blood cell-alloimmunized pregnancies.', 'In an 11-year period, 213 fetuses received 599 intrauterine transfusions. The outcome of 208 pregnancies, including two pairs of twins, was analyzed in a retrospective study. Eighty fetuses demonstrated ultrasonographic signs of hydrops at the start of treatment; 42 of these were classified as mildly hydropic and 38 were classified as severely hydropic. Reversal of hydrops as a result of treatment, survival, and neonatal morbidity was studied.', 'The overall survival rate of fetuses with hydrops was 78%. Of the fetuses with mild hydrops, 98% survived, whereas in cases of severe hydrops the survival rate was 55%. Intrauterine reversal of hydrops occurred in 65% of the fetuses with hydrops. The reversal rate was 88% in fetuses with mild hydrops and 39% in fetuses classified as severely hydropic. After reversal of hydrops, almost all of the fetuses survived (98%), whereas in cases of persistent hydrops outcome was unfavorable, with a survival rate of 39% for all fetuses and 26% for fetuses classified as severely hydropic.'] Is the severity of immune fetal hydrops predictive of fetal outcome after intrauterine treatment?