The Impact of Noninvasive Prenatal Testing on the Practice of Maternal–Fetal Medicine

Identifying pregnancies at increased risk for aneuploidy has been a part of the practice of maternal–fetal medicine for several decades. Originally, women were identified based on maternal age alone and given the option of diagnostic testing via chorionic villus sampling (CVS) or amniocentesis to determine the fetal karyotype. Recently, maternal serum screening tests, with or without ultrasound findings, were developed for use in the general obstetrical population to identify at-risk pregnancies.1,2 Since CVS and amniocentesis carry a risk for miscarriage, research has continued to pursue other means of obtaining the fetal genetic complement. Recently, three separate multicenter trials of noninvasive prenatal testing (NIPT) showed that analyzing cell-free DNA in the maternal circulation results in a highly sensitive and specific testing option for fetal aneuploidy, with 98 to 100% detection rate at < 0.3% false-positive rate for Down syndrome and 97 to 100% detection rate at < 0.28% false-positive rate for trisomy 18.3–6 The detection rate for trisomy 13 varied more widely across studies, ranging from 79 to 92% with < 1% false-positive rate.4,6 Advances in prenatal screening for aneuploidy have led to a decrease in invasive testing and an increase in screening in the