First-trimester contingent screening for trisomies 21, 18 and 13 by fetal nuchal translucency and ductus venosus flow and maternal blood cell-free DNA testing

Objective: To examine performance of screening for major trisomies by a policy of first-line assessment of risk according to maternal age, fetal nuchal translucency thickness (NT) and ductus venosus pulsatility index for veins (DV-PIV) followed by cell-free DNA (cfDNA) testing in pregnancies with an intermediate risk. Methods: We estimated the distribution of risks based on maternal age, fetal NT and DV-PIV in a dataset of 86 917 unaffected and 491 trisomic pregnancies undergoing prospective screening for trisomies. Performance of screening for trisomies by cfDNA testing was derived from a meta-analysis of clini…