NT mainly examines the thickness of the fetal nuchal translucency zone, which is the thickness of fluid accumulation in the subcutaneous tissue of the posterior nuchal region of the fetus. The degree of fluid accumulation in this area can reflect the degree of fetal metabolism, and can assess whether the fetus has chromosomal abnormalities resulting in malformations, such as spinal malformations, congenital heart disease, structural malformations of the heart, etc., all of which can be assessed in the detection of fetal nuchal translucency thickness, screening out the indicators of abnormal fetuses, the need for further examination; and also to determine whether the fetus suffers from Down syndrome, which is part of the early Down syndrome screening It is an early Down’s syndrome screening test. Understanding the following will help the NT test go more smoothly: 1. NT test can be done from the abdomen or from the vagina, there is no special requirement, no need for fasting or holding urine; 2. The most important thing is to grasp the time to do the NT test, because the NT test has higher chances of detecting abnormality and higher accuracy when it is done at (11-13) weeks + 6 days, and once it is over this time, the accuracy may be significantly lower. Therefore, it is important to take the test within the time period stipulated by the doctor, especially for pregnant women with less regular periods, it is better to take an ultrasound to determine the week of pregnancy at an early stage, so as not to miss the time of the NT test.