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.