Early fetal sex determination using micro-volume of maternal plasma

Cell-free fetal DNA (cffDNA) represents around 10% of total cell-free DNA in maternal circulation, and it is detectable in the blood from the fifth week of pregnancy. It allows us to obtain genetic information about the foetus without the necessity of using invasive procedures that imply a risk of miscarriage, such as amniocentesis and chorionic villous sampling. This makes the technique very useful in the identification of genetic pathologies.
Another common application of this technique is early sex determination, usually performed through PCR-based techniques, either end-point PCR or qPCR. While the most usual method for sex determination, sonography, is not reliable during the first trimester of pregnancy, the analysis of cffDNA allows us to perform gender determination as early as 9 weeks gestation. It can detect specific sequences of the Y-chromosome with great accuracy, which, if detected, would mean that the foetus is a male.