An NT scan is a common screening test that is done during the first trimester of pregnancy i.e., between 11 – 14 weeks. This scan measures the size of the clear tissue, called the nuchal translucency (NT), at the back of the baby’s neck. It is a sonographic prenatal screening scan to detect chromosomal abnormalities in a fetus. The results of a nuchal translucency scan along with the blood tests and maternal age will tell if the fetus is at low, intermediate or high risk of a chromosomal abnormality.
If the results come as high risk, it is advisable that the mother undergoes an invasive test like amniocentesis or chorionic villus sampling (CVS) to confirm the diagnosis.
The NT scan is performed usually transabdominally with a full bladder but occasionally the nuchal translucency can only be seen by transvaginal scan. It is often combined with a blood test, the double marker. The scan and the blood test together constitute the first trimester screening test.