First of all, we should clearly understand the significance of Down’s syndrome screening, which is an important screening tool to detect DNA defects in newborns. It is a test that calculates the risk of having a fetus with congenital defects by taking maternal serum, detecting the concentration of alpha-fetoprotein, chorionic gonadotropin and free estriol in maternal serum, and taking into account the maternal due date, weight, age and gestational week at the time of blood collection. The test is used to calculate the risk of having a fetus with congenital defects, taking into account the expected date of delivery, weight, age and week of pregnancy. Currently, there are two methods of screening for chromosomal disorders in China: the traditional Down screening (twice, in early pregnancy and in mid pregnancy) and the non-invasive DNA prenatal genetic testing. The best time to get tested is between 15-20 weeks of pregnancy, and the result is a score, which is the chance of having an abnormality, and when the chance is too high, we usually call it high-risk. However, mothers with a high risk of Down’s syndrome do not need to worry too much. According to the traditional treatment routine, pregnant women with a high risk of Down’s syndrome should undergo amniocentesis, which is still the gold standard for fetal congenital defects. However, amniocentesis is an invasive and risky test that requires the patient and family to make their own decisions. In recent years, with the rapid development of genetic technology, some non-invasive DNA technologies have begun to emerge. Some foreign literature reports that the accuracy of non-invasive DNA testing has reached more than 95% of that of amniocentesis. The reason for recommending Down’s syndrome screening is simple: although the test is only a “probability”, if you don’t check, the probability of having a Down’s child is 100% if you are really hit.