Clinical application of fetal sex determination using cell-free fetal DNA in pregnant carriers of X-linked genetic disorders.

As the first step in prenatal diagnosis of X-linked genetic disorders, chorionic villus sampling (CVS) for fetal sex determination is generally performed at 11-13 weeks of gestation. However, as the procedure-related miscarriage rate of CVS is 0.5-1.0%, non-invasive methods such as PCR of cell-free fetal DNA (cff-DNA) in maternal plasma are preferable. Here, we determined fetal sex at 9-12 weeks of gestation using PCR of cff-DNA in three pregnant carriers of Duchenne muscular dystrophy. The fetal sex was accurately determined in all three cases, as confirmed by ultrasound and amniocentesis at 16 weeks (for the two female fetuses) and CVS at 12 weeks (for the one male fetus). This procedure could avoid unnecessary CVS in female fetuses.