NT ultrasound is mainly one of the indicators used to screen for Down’s syndrome. NT, also known as posterior cervical zona pellucida scan, is a normal subcutaneous fluid accumulation between the fetal nuchal collar and the skin, and is an ultrasound sign that can be seen in all fetuses in late early pregnancy. The NT ultrasound test can guide the need for chromosomal screening and further determine the risk of Down’s syndrome. This is when the fetal nervous system has basically differentiated and it is easier to determine whether the thickness of the nuchal translucency is normal through ultrasound. In Down’s syndrome, the fetus will have subcutaneous fluid accumulation, so the skin at the back of the neck will be thicker. The normal value of NT is usually 2.5mm, some hospitals are 3mm, if NT is thickened, amniocentesis is recommended. The NT ultrasound test in early pregnancy is mainly used to assess the risk of Down’s syndrome and cannot detect all the abnormal structures, and fetal echocardiography is recommended in mid pregnancy. If abnormal fetal development is confirmed, termination of pregnancy may be required.