First-Trimester Contingent Screening for Trisomies 21, 18 and 13 by Biomarkers and Maternal Blood Cell-Free DNA Testing

<b><i>Objective:</i></b> To examine potential performance of screening for trisomies by cell-free (cf) DNA testing in maternal blood contingent on results of first-line testing by combinations of fetal translucency thickness (NT), fetal heart rate (FHR), ductus venosus pulsatility index (DV PIV), and serum-free β-human chorionic gonadotropin (β-hCG), pregnancy-associated plasma protein-A (PAPP-A),...