Paternal RHD hemizygosity may be overestimated. Thus, we recommend that RHD zygosity be established by molecular analysis of the RHD breakpoint. Cultured amniocytes should be reserved for testing if the amniotic fluid-derived DNA is inconclusive due to PCR amplification failure. We use PCR-RFLP genotyping methods for RHCE*E/RHCE*e (Rh E/e), KEL1/KEL2 (K/k), FYA/FYB (Fy(a/b)), and JKA/JKB (Jk(a/b)).