Identification of trisomy 18, trisomy 13, and Down syndrome from maternal plasma

Abstract

Jean Gekas,1,2 Sylvie Langlois,3 Vardit Ravitsky,4 François Audibert,5 David-Gradus van den Berg,6 Hazar Haidar,4 François Rousseau2,71Prenatal Diagnosis Unit, Department of Medical Genetics and Pediatrics, Faculty of Medicine, Laval University, Québec City, Quebec, Canada; 2Department of Medical Biology, Centre Hospitalier Universitaire de Québec, Québec City, Quebec, Canada; 3Department of Medical Genetics, University of British Columbia, Vancouver, Canada; 4Bioethics Program, Department of Social and Preventive Medicine, School of Public Health, University of Montreal, Montreal, Canada; 5Department of Obstetrics and Gynecology, Sainte Justine Hospital, Montreal, Canada; 6Department of Social and Preventive Medicine, 7Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Québec City, Quebec, CanadaAbstract: Current prenatal diagnosis for fetal aneuploidies (including trisomy 21 [T21]) generally relies on an initial biochemical serum-based noninvasive prenatal testing (NIPT) after which women who are deemed to be at high risk are offered an invasive confirmatory test (amniocentesis or chorionic villi sampling for a fetal karyotype), which is associated with a risk of fetal miscarriage. Recently, genomics-based NIPT (gNIPT) was proposed for the analysis of fetal genomic DNA circulating in maternal blood. The diffusion of this technology in routine prenatal care could be a major breakthrough in prenatal diagnosis, since initial research studies suggest that this novel approach could be very effective and could reduce substantially the number of invasive procedures. However, the limitations of gNIPT may be underappreciated. In this review, we examine currently published literature on gNIPT to highlight advantages and limitations. At this time, the performance of gNIPT is relatively well-documented only in high-risk pregnancies for T21 and trisomy 18. This additional screening test may be an option for women classified as high-risk of aneuploidy who wish to avoid invasive diagnostic tests, but it is crucial that providers carefully counsel patients about the test's advantages and limitations. The gNIPT is currently not recommended as a first-tier prenatal screening test for T21. Since gNIPT is not considered as a diagnostic test, a positive gNIPT result should always be confirmed by an invasive test, such as amniocentesis or chorionic villus sampling. Validation studies are needed to optimally introduce this technology into the existing routine workflow of prenatal care.Keywords: prenatal diagnosis, Down syndrome, noninvasive prenatal testing, cell-free fetal DNA, informed consent, reproductive autonomy