The NT test is mainly to see the thickness of the posterior nuchal translucency layer, which is mainly used to assess the risk of fetal malformation and to determine the development of the baby. NT test is important as a means of early screening, as follows It provides a reliable basis for eugenics. Generally NT value less than 2.5mm is normal, NT greater than 2.5mm will increase the chance of unhealthy fetus, suggesting increased risk of fetal chromosomal abnormalities. The NT test results can be used to assess whether the fetus is suffering from Down’s syndrome, and can also be used to monitor the fetus’ health condition with the results of 4D ultrasound and Down’s screening, forming a multiple insurance; 3. The fetus will also dance around, which is worth treasuring as it is not easy to see in the later examinations due to the increase of fetus size during pregnancy. As mentioned above, the NT test cannot determine the sex of the fetus. Moreover, it is currently illegal to conduct fetal sex determination for non-medical needs, and parents are advised to be objective and fair.