Following the introduction of noninvasive prenatal testing (NIPT) at the Maine Medical Center in Portland, the number of invasive prenatal diagnostic procedures decreased.
In a retrospective study, Joseph R. Wax, MD, and colleagues gathered statistics on the rates of genetic counseling, invasive prenatal diagnosis, and trisomy 21 detection among women who were at increased risk for aneuploidy. These rates were compared before and after the availability of NIPT.
The study included 1,046 women who underwent NIPT between June 1, 2012, and February 1, 2013, as well as 1,464 women who would have been eligible for NIPT if it had been available between December 1, 2010, and November 30, 2011. All women were aged 35 years or older and had ultrasound findings suggestive of increased risk of aneuploidy, a positive aneuploidy screen, prior trisomic fetus, or parental balanced translocation with increased risk for trisomy 13 or 21. One laboratory performed NIPT after patients received genetic counseling. The two groups were compared by maternal demographics, aneuploidy risk factors, rates of genetic counseling, invasive diagnostic procedures, and trisomy 21 detection.1
Results of the study A total of 33 fetuses with trisomy 21 were identified by positive aneuploidy screening. After the introduction of NIPT, genetic counseling for aneuploidy risk increased (adjusted odds ratio [aOR], 1.77; P <.0001). However, the overall use of invasive diagnostic testing (aOR, 0.42; P <.0001), including amniocentesis (aOR, 0.37, P <.0001), decreased, although the prenatal diagnosis of trisomy 21 remained similar (88% vs 100%; P = .86).1
Dr. Wax and colleagues concluded that, “NIPT in clinical practice uses more genetic counseling resources but requires significantly fewer invasive procedures to maintain the detection rates of trisomy 21.”1