BACKGROUND: It is hypothesized that male fetuses are more severely affected by fetomaternal alloimmunization to D antigen than female fetuses.

STUDY DESIGN AND METHODS: One hundred four consecutive pregnancies with single D+ fetuses (51 males, 53 females) and maternal anti-D titers >16 were analyzed retrospectively.

RESULT: Sixty fetuses (58%) received intrauterine transfusions. Male fetuses required more transfusions than females (5.0 vs. 2.0, p = 0.0001). At the initial transfusion, male fetuses had a lower gestational age (24.5 vs. 31.0 weeks, p = 0.0007), cord blood hemoglobin content (6.45 vs. 8.75 g/dL, p = 0.01), and hematocrit (19.8 vs. 26.8%, p = 0.004) than female fetuses. After adjustment for maternal gravidity, parity, and history of affected offspring, the odds ratio for development of hydrops by male fetuses was 13.1 (95% Cl 2.69–63.6, p = 0.001). Perinatal mortality was higher in male (18%) fetuses than in female (6%) (adjusted odds ratio for males 3.38; 95% Cl 0.59–19.46, p = 0.17).

CONCLUSION: Male fetuses are particularly affected by maternal alloimmunization to D and require more intense antepartum surveillance than female fetuses.