Noninvasive prenatal testing: impact on genetic counseling, invasive prenatal diagnosis, and trisomy 21 detection

The aim of this study was to compare rates of genetic counseling, invasive prenatal diagnosis, and trisomy 21 detection among women at increased risk for aneuploidy, before versus after the availability of noninvasive prenatal testing (NIPT).

This institutional review board-exempt retrospective study included all women who had an ultrasound (US) examination between 10 0/7 and 21 6/7 weeks' gestation and were eligible for NIPT (ie, age ≥35 years, US findings suggestive of increased aneuploidy risk, positive aneuploidy screen, prior trisomic fetus, parental balanced translocation with increased risk for trisomy 13 or 21) between June 1, 2012 and February 1, 2013. NIPT was performed by a single laboratory after patients received genetic counseling. We also identified a comparison group of women evaluated between December 1, 2010 and November 30, 2011, who would have been eligible for NIPT had it been available. The two groups were compared for maternal demographics, aneuploidy risk factors, rates of genetic counseling, invasive diagnostic procedures, and trisomy 21 detection.

The before-NIPT and after-NIPT groups contained 1,464 and 1,046 subjects, respectively. All 33 fetuses with trisomy 21 in the two groups were identified by positive aneuploidy screening. After the introduction of NIPT, genetic counseling for aneuploidy risk increased (adjusted odds ratio [aOR], 1.77 [1.49-2.11]; p < 0.0001) and the overall invasive diagnosis (aOR, 0.42 [0.32-0.55]; p < 0.0001), including amniocentesis (aOR, 0.37 [0.27-0.52], p < 0.0001), decreased, whereas the prenatal diagnosis of trisomy 21 remained similar (88% versus 100%; p = 0.86).

NIPT in clinical practice uses more genetic counseling resources but requires significantly fewer invasive procedures to maintain the detection rates of trisomy 21.