Noninvasive prenatal RHD genotyping by real-time polymerase chain reaction using plasma from D-negative pregnant women

Objective Prenatal noninvasive determination of fetal Rh status is an important aid to the management of hemolytic disease of the fetus and newborn. We performed real-time polymerase chain reaction on fetal DNA derived from maternal plasma to determine fetal Rh status. Study design Cell-free plasma DNA from 98 D-negative pregnant women was tested for the presence of exons 4, 5, and 10 of RHD. The presence of fetal DNA was confirmed by detection of SRY or biallelic insertion/deletion polymorphisms in the maternal plasma and buffy coat. Results Seventy-two D-positive infants and 26 D-negative infants were determined by serologic studies. All 3 RHD exon sequences were detected in 68 of 72 mothers of D-positive infants. The presence of fetal DNA in mothers of D-negative infants was confirmed in all 10 boys and in 14 of 16 girls. Conclusion Fetal RHD genotyping in this study correctly predicted fetal Rh status in 92 of 98 (94%) cases.