Nuchal translucency (NT) is the sonographic measurement of the fluid-filled space at the back of the fetal neck, performed between 11 weeks 0 days and 13 weeks 6 days. An increased NT measurement is associated with an elevated risk of chromosomal abnormalities including trisomy 21 (Down syndrome), trisomy 18, trisomy 13, and Turner syndrome, as well as structural cardiac defects. NT measurement is a technically demanding skill requiring specific training and quality review programs such as those administered by the Nuchal Translucency Quality Review (NTQR) program.