NT scan

Image courtesy: Dr Ayush Goel

NT scan is an antenatal ultrasound which is advised for early screening of the baby to look for risk of trisomies (a type of genetic abnormality). It is performed between 11-13.6 weeks gestation age. Few anomalies may also show up at this early gestation. 
It aims at evaluation of fluid collection at the nape of neck of the baby. However this must be done keeping in mind the strict guidelines because the risk estimation is not valid if the guidelines are not followed. Additional markers (NB, DV, TR) should also be looked for to increase the detection rate and reduce false positive rates of the test.

The test must be combined with a blood test (Dual marker test) which further increases the detection rate of trisomies.
It is estimated that combining NT scan with Dual marker, may increase the detection rate above 95% and reduce false positive rate below 3%.

Note: NT scan is a screening test and not a diagnostic test.