The NT test is not the same as the Down’s syndrome test, but is an ultrasound test performed between 11 and 14 weeks of pregnancy to determine if the thickness of the posterior nuchal translucency is normal. If it is too thick, there is a possibility of fetal neural tube abnormality; if it is normal, there is a lower chance of neural tube abnormality. Down’s syndrome screening is divided into early and mid-term Down’s syndrome screening, which is mainly performed by drawing blood during the early and mid-term of the patient’s pregnancy to determine whether the patient’s fetus is likely to have trisomy 18, trisomy 21 and other intellectual problems. If the risk is high, the chances of this possibility will be high and further non-invasive genetic tests or amniocentesis will be needed for confirmation. If all are normal, it proves that the patient’s fetus has a low chance of developing the disease, but it cannot be completely ruled out. If the patient has a family history of the disease, in this case the patient must undergo amniocentesis for further confirmation.