Definition of NT/ NB SCAN: How it Works NT/NB scan, short for nuchal translucency/nasal bone scan, is a prenatal screening procedure performed around 11 to 14 weeks of pregnancy. It assesses the risk of chromosomal abnormalities, particularly Down syndrome. The procedure involves ultrasound imaging to measure the thickness of the nuchal translucency (fluid accumulation at the back of the fetal neck) and the presence/absence of the fetal nasal bone. Higher NT thickness and absence of the…