NT- stands for Nuchal translucency.
Necessary in screening for Trisomies such as T21, T18, T13. It is measured when the pregnancy reaches 11-13weeks + 6days. Or the CRL is within 54-84mm. As it is just a screening, it does not indicates that the patient with NT measured >3mm is going to have abnormal baby. Because this is just a screening. If the NT is > 3mm the patient has to undergo minor procedure to aspirate a small volume of liquor for QF-PCR or karyotyping to see clearly the chromosomes of the fetus. These test will diagnosed the fetus.