Abnormal Down’s syndrome means that the fetus has a higher probability of having Down’s syndrome. However, the Down’s syndrome test is affected by height, weight and gestational week, and the next step of examination, such as amniocentesis, non-invasive DNA, ultrasound, etc., needs to be performed according to the abnormal items and the degree of abnormality. If the risk of trisomy 21 or trisomy 18 is high, then amniocentesis must be done to clarify the condition, and the results of amniocentesis are more accurate. If it is a critical risk, further clarification is required by non-invasive DNA, which is more accurate. If the open neural tube malformation is at high risk, in this case further systematic ultrasound is needed for clarification, and amniocentesis or non-invasive DNA is not required. In the case of an abnormal Down’s syndrome screening, the next test should be performed as prescribed by the doctor to screen for the risk of Down’s syndrome.