Background To evaluate the relationship between obstetric history and Rh(D) alloimmunization severity, employing the gestational age at the Wrst intrauterine fetal transfusion (IUT) as an indicator of this severity. Methods From 1996 to 2006, Rh(D) alloimmunized pregnancies submitted to IUT had their data assessed. Gestational age at the Wrst IUT was modeled as a linear outcome. The associations between obstetric history variables, anti- Rh(D) antibodies titer and gestational age at the Wrst IUT were analyzed. Statistics are presented with 95% conWdence intervals (P < 0.05). Results A total of 82 non-hydropic anemic fetuses, ensuing in 92.7% (n = 76) of perinatal survival, were submitted to IUT. Nineteen (23,2%) pregnant women did not present with any previous stillbirth, neonatal death, IUT, hydrops or neonatal exchange transfusion (group 1); and 63 (76.8%) reported at least one of these events (group 2). Gestational age at the Wrst IUT diVered signiWcantly between the groups (P = 0.0001). For group 1, it ranged from 24 to 35 weeks (median 32.5 weeks), whereas for group 2 it ranged from 19 to 34 weeks (median 27 weeks). In the multivariated analysis, previous neonatal death (P = 0.040), previous IUT (P = 0.000) and previous neonatal exchange transfusion (P = 0.036) were independently associated with the gestational age at the Wrst IUT. Conclusions The evaluation of the obstetrical history is an important diagnostic tool for predicting Rh(D) alloimmunization severity. Alloimmunized pregnant women who reported previous neonatal death(s), neonatal exchange transfusion(s) or IUT(s) should receive a closer fetal surveillance due to the risk of a higher rate of fetal hemolysis and the need of an earlier IUT.