Use of Cell-free DNA to Screen for Down's Syndrome

Standard prenatal screening for trisomy 21 (Down's syndrome) is based on a combination of maternal age, maternal serum biomarkers, and fetal ultrasonographic findings. Such screening can identify 70 to 90% of fetuses with trisomy 21 with a false positive rate of 2 to 5%.1 Screening that is based on analysis of cell-free DNA (cfDNA) in maternal plasma is now available through commercial providers in more than 60 countries around the world.2 However, although the sensitivities and specificities obtained through this approach are high,3 there is still much debate as to how this screening should be offered.Most large studies evaluating . . .