20 years experience of RhD alloimmunization at a state referral center in Rio de Janeiro: a study of 481 cases.

Objective: This study sought to analyze the profile of fetuses, newborns and pregnant women with alloimmunization (anti-RhD) referred to and treated over the twenty years since the launch of the Rio de Janeiro State. Methods: An observational, retrospective, descriptive study was conducted, with data obtained by analyzing the medical records of 481 mothers and their newborns. The study cohort consisted of pregnancies affected by RhD alloimmunization who delivered between March 2004 and March 2024 in Rio de Janeiro. Results: The absolute number of cases declined over the study period. Only 5.2% of the cohort began prenatal care in the first trimester of pregnancy and more than half (51.6%) of women arrived at the referral center in the third trimester. 40% of the women had prior severe HDFN. During this period, 422 intrauterine transfusions were performed on 71 fetuses, an average of 5.9 transfusions per patient. Infant mortality; was low, with 4% stillborn or evolving to neonatal mortality. Conclusion: The trend observed over the last 20 years is a reduction in the absolute number of HDFN cases which is perhaps more related to reproductive issues, particularly the sharp reduction in parity in our state, rather than to the implementation of alloimmunization prophylaxis.