Management and outcome of fetomaternal Rh alloimmunization in twin pregnancies

Between 1987 and 1996, nine twin pregnancies with fetomaternal Rh alloimmunization were delivered at our institution. Eight pregnancies were dizygotic, and the fetal blood groups were different in 3 cases. The remaining pregnancy was monozygotic and monochorionic-diamniotic. Intravenous fetal exchange transfusion was performed in five pregnancies, up to five times in each twin in one pregnancy. No fetal death occurred. The average gestational age at birth was 35 (range 33-37) weeks. The hemoglobin level was 13.2 (range 9.2-16.5) g/dl. Fetomaternal Rh alloimmunization in twin pregnancy is according to zygosity; each fetus has to be treated separately, except in case of transplacental communication.