Problems Facing the Advanced Reproductive Age Population – Birth Defects Eugenic issues are highlighted in the advanced age population, and AMA is a high risk factor for chromosome number abnormalities in the fetus. Those whose first pregnancy is of advanced age tend to place great importance on prenatal diagnosis and enter the prenatal diagnostic process earlier. In contrast, those who are having another child, who think they have had healthy babies, do not pay much attention to prenatal diagnosis. Currently, amniocentesis karyotyping is still the most reliable method of prenatal diagnosis of AMA trisomy, and will continue to be the “gold standard” for diagnosis. However, because amniocentesis is an invasive procedure that is difficult to accept and carries a certain risk of causing miscarriage, mid-pregnancy serum marker screening will remain the mainstay of prenatal screening for trisomy 21 for quite some time. How to choose the best screening protocol to maximize the detection of chromosomally abnormal fetuses, minimize the rate of interventional prenatal diagnosis, and improve the cost-effectiveness ratio of prenatal screening and diagnosis is a practical problem faced by obstetrics departments in China at present. Non-invasive peripheral blood fetal DNA testing is a new method of prenatal screening for trisomy 21 diseases with a wide time window, high detection rate and low false-positive rate, but it is characterized by high testing cost and high technical requirements, and it is a prenatal screening technology that “approximates to the level of prenatal diagnosis with precise target diseases”.