Clinical Significance of Maternal Anti-D Antibody Titers in Severe RhD Alloimmunization Requiring Intrauterine Transfusion: A Tertiary Referral Center Experience.

Background: Maternal anti-D antibody titers are routinely used for risk stratification in RhD alloimmunization before the development of fetal anemia. However, their association with disease severity and perinatal outcomes among pregnancies that have already progressed to severe fetal anemia requiring intrauterine transfusion (IUT) remains unclear. This study aimed to investigate the association between maternal anti-D antibody titers, disease severity, and perinatal outcomes in pregnancies complicated by severe RhD alloimmunization requiring IUT. Methods: This retrospective cohort study included 38 RhD-alloimmunized pregnancies complicated by severe fetal anemia and managed with IUT at a tertiary referral center between January 2017 and December 2022. Maternal characteristics, anti-D antibody titers, presence of hydrops fetalis, IUT characteristics, delivery data, neonatal outcomes, and mortality were evaluated. Maternal anti-D antibody titers were analyzed in relation to disease severity and perinatal outcomes. Results: Hydrops fetalis was present in 24 fetuses (63.2%). The mean maternal age was 30.3 ± 4.8 years, and the mean gestational age at diagnosis was 23.5 ± 5.8 weeks. Maternal anti-D antibody titers were significantly higher in pregnancies complicated by hydrops fetalis than in non-hydropic pregnancies (p = 0.014). No significant associations were observed between maternal anti-D antibody titers and intrauterine fetal demise, neonatal mortality, neonatal intensive care unit admission, Apgar scores, or the number of IUT procedures. Conclusions: Among pregnancies with severe RhD alloimmunization requiring intrauterine transfusion, higher maternal anti-D antibody titers were associated with hydrops fetalis, suggesting an association with disease severity. However, no statistically significant associations were observed between maternal anti-D antibody titers and other evaluated perinatal outcomes in this high-risk cohort. These findings indicate that, once severe fetal anemia requiring IUT has developed, maternal anti-D antibody titers should be interpreted alongside fetal Doppler surveillance and comprehensive clinical assessment rather than as independent predictors of perinatal prognosis.