It is based on the detection of certain genes specific to the male in the mother’s blood. From the 5th week of gestation, free fetal DNA begins to be observed in the mother’s blood plasma and the concentration increases as the pregnancy progresses, about 30% each week of gestation. All fetal DNA accounts for between 5% and 7% of total free DNA in maternal blood.
The test consists of a simple drawing of blood, and within about a week, the results are obtained and a reliability close to 100%.