Fetal gender determination using real-time quantitative polymerase chain reaction analysis of maternal plasma.

BACKGROUND AND PURPOSE: Cell-free fetal DNA in maternal blood is a promising non-invasive alternative for prenatal diagnosis. The goal of this study was to determine fetal sex with maternal plasma in pregnant women without previous male offspring. METHODS: Blood samples (3 mL) were collected at 6 to 16 weeks' gestation from 56 healthy pregnant women without previous male offspring. There were 23 pregnancies with male fetuses and 33 pregnancies with female fetuses. DNA was extracted from plasma and qualitative analysis of the sex-determining region Y (SRY) gene sequence on the Y chromosome (SRY-3317T) with dual-labeled fluorescent TaqMan probe using real-time quantitative polymerase chain reaction (PCR) was performed. RESULTS: In the 56 successfully assayed samples, SRY-positive signals were detected in 20 samples of the 23 pregnancies with male fetuses. None of the 33 successfully assayed samples from women bearing female fetuses yielded a positive signal. CONCLUSIONS: Because of its high correct prediction rate, fetal gender determination with maternal plasma using real-time quantitative PCR can be used as a pre-test to avoid unnecessary chorionic villus sampling for pregnancies at risk of fetal sex-associated disorders.