Fetal screening is a dynamic process, as the degree of fetal development is different in each period, the corresponding screening should be performed at the corresponding time to achieve better results. 1. 11-13 weeks of pregnancy: NT test, also known as posterior cervical zona pellucida test, is generally performed by ultrasound to check the thickness of the fetal cervical zona pellucida, which is mainly used for early screening to assess whether the fetus has Down syndrome. 2. 14-18 weeks of pregnancy: Down’s syndrome screening can be performed, mainly to check whether the fetus has chromosomal disorders, the test is performed by intravenous blood sampling. 2. 14-18 weeks of gestation: Down’s syndrome screening can be performed, mainly to check whether the fetus has chromosomal disorders, and the test is performed by intravenous blood sampling. If the result of Down’s syndrome screening shows high risk, for pregnant women <35 years old, non-invasive DNA testing of peripheral blood can be done for prenatal diagnosis, while for pregnant women >35 years old, amniocentesis is recommended to determine whether there are chromosomal diseases in the fetus; 3. 22-24 weeks of pregnancy: Systematic teratology examination can be performed, and each important organ of the fetus can be systematically examined through ultrasound, and anencephaly, open spina bifida, abdominal wall defect can also be screened. The ultrasound can also screen for anencephaly, open spina bifida, abdominal wall defect, heart malformation, lethal chondrodysplasia, etc.; 4. 28-30 weeks of gestation: minor teratology ultrasound can be performed to evaluate the growth and development of various important organs and organs of the fetus again.