Accuracy of Fetal Gender Determination by Analysis of DNA in Maternal Plasma

In 1997, Lo et al. (1) first described the presence of fetal DNA in maternal plasma and serum. Cell-free DNA offered a new source of fetal genetic material for noninvasive prenatal diagnosis. They developed a real-time, quantitative PCR assay to measure the concentration of fetal DNA and analyzed SRY, a single-copy Y-chromosome-specific sequence, to quantify the number of genome-equivalents per milliliter of blood when a woman carries a male fetus (2). The results revealed that the concentrations of fetal DNA in maternal plasma DNA during the first and third trimesters were 3.4% and 6.2%, respectively. They estimated a mean of 25.4 copies of fetal DNA circulates per milliliter of maternal plasma samples during early pregnancy. They also demonstrated that after delivery, cell-free fetal DNA is cleared very rapidly from the maternal circulation, with a half-life in the order of minutes (3). Thus, the relatively high concentration of fetal cell-free DNA suggests that extensive and time-consuming fetal DNA enrichment procedures would not be necessary when using fetal DNA from maternal plasma for diagnostic purposes. Although the potential of fetal cell-free DNA analysis for the prenatal diagnosis of fetal gender (2) and rhesus D status (4)(5) has been presented, the accuracy of prenatal diagnosis has not been described. If fetal gender could be determined, the number of invasive procedures required to determine X-linked genetic disorders would be reduced. The present study evaluated the diagnostic accuracy of fetal gender determination using cell-free DNA from maternal plasma obtained at early gestation. Pregnant women (n = 302), carrying a single fetus between 7 and 16 weeks of gestation, …