In a study presented this week at the Society for Maternal-Fetal Medicine’s annual meeting, The Pregnancy Meeting, researchers report that noninvasive prenatal testing detected 83.2% of chromosomal abnormalities normally picked up by invasive diagnostic testing such as chorionic villus sampling (CVS) or amniocentesis. Noninvasive prenatal testing (NIPT) using cell free DNA provides accurate screening for the common trisomies, including trisomy 13 (Patau syndrome), 18 (Edwards syndrome), and 21 (Down syndrome).
In this study, Rare Chromosome Abnormalities Detected by Current Prenatal Screening Compared to Expected Performance using Non-Invasive Prenatal Testing (NIPT), 68,990 of 1,324,607 women tested positive for trisomy 18 or 21 when they underwent prenatal screening as part of the California Prenatal Screening Program between March 2009 and December 2012. Invasive diagnostic testing with CVS or amniocentesis was performed on 26,059 women who tested positive, and 2,993 were found to have abnormal results. Of those chromosomal abnormalities, 2,489 (83.2%) were abnormalities that would be detectable with NIPT, while 16.8% percent were less common aneuploidies that would not be detected.
Study co-author Mary Norton, MD, says that more of the abnormal results were detectable in the women over 40, who are at higher risk for trisomy 13, 18 or 21. Conversely, fewer of the abnormalities in younger women would be detected by NIPT, as the risk for common trisomies is lower in this group, while the rare aneuploidies are not typically associated with maternal age.
“With this test,” Norton continues, “the patient makes a tradeoff between NIPT, which is noninvasive and detects most but not all chromosome abnormalities—and is somewhat better in older women—and amniocentesis or CVS, which detect more chromosome abnormalities but with a small risk of miscarriage due to the procedure.” Read the article outline.
