Nuchal translucency (NT) screening is a specialized first-trimester ultrasound performed between 11 and 14 weeks gestation to measure the fluid-filled space at the back of the fetal neck. When combined with maternal serum biochemistry (PAPP-A and free β-hCG), NT measurement is part of the combined first-trimester screening protocol for chromosomal abnormalities including Down syndrome (trisomy 21), trisomy 18, and trisomy 13.
The examination requires precise technique: the fetus must be in a neutral position, the measurement must be taken at the widest point of the translucency, and calipers must be placed correctly. Sonographers performing NT measurements must complete specific training and quality review programs. Additional markers such as nasal bone presence and ductus venosus flow may be assessed concurrently.
NT measurement is regulated by the Nuchal Translucency Quality Review (NTQR) program and other bodies that require periodic image submission and proficiency demonstration. Sonographers performing NT screening typically hold RDMS credentials with OB/GYN specialty and complete dedicated NT training. This examination is performed in maternal-fetal medicine offices, OB/GYN practices, and hospital antenatal testing units.