If the clinical NT value is 3.1mm by ultrasound, further non-invasive DNA test or amniocentesis is needed because the NT value is less than 3.0mm under normal circumstances. It is recommended to do amniocentesis in this case, mainly to exclude fetal chromosomal abnormalities, and it is best to go to a tertiary care hospital for this test. After the pregnancy, it is very important to have the screening tests, such as NT and Down’s syndrome screening. The 4D ultrasound between 23 and 28 weeks of pregnancy is very important. It is advisable to follow the doctor’s instructions for regular check-ups to rule out the possibility of malformations and to deal with any abnormalities in time.