Genetic testing is the examination of genes and DNA sequences through blood and body fluids to rule out chromosomal or genetic abnormalities, to help reduce the birth of malformed children, and to diagnose genetic diseases. If you are preparing for pregnancy, you can be tested before conception, or if you want to diagnose your own disease, there is no requirement for the timing of the test, and you can be tested at any time. Common clinical genetic testing programs include: i. Serum biochemical testing: 1. Basic principle: Biochemical testing is performed by taking blood and combining it with age, weight and gestational week to determine the presence of genetic defects, which can be used to predict the risk of fetuses with trisomy 21, trisomy 13, trisomy 18 and neural tube defects. In addition, serum biochemical tests can also diagnose familial idiocy, phenylketonuria, cystic fibrosis, etc.; 2. Testing time: Usually the test is performed in early pregnancy at (11-13) weeks plus 6 days, and in mid-pregnancy at 15-20 weeks. If the general population is examined for diseases, there is no time limit. Second, DNA testing: 1. Basic principle: By collecting peripheral blood and performing bioinformatics analysis, it can clarify the presence of genetic diseases caused by genetic abnormalities, and can also be used to assess the risk rate of fetuses suffering from trisomy 21, trisomy 13, and trisomy 18 syndromes. In addition, DNA testing can be used to identify monogenic genetic disorders such as Huntington’s disease. 2. Timing of testing: Testing can usually be performed from 10 weeks of gestation, with the optimal gestational week being (12-22) weeks plus 6 days. In case of disease screening for the general population, there is no time limit. Amniocentesis: 1. Basic principle: ultrasound-mediated extraction of amniotic fluid from the amniotic cavity to obtain fetal cells or fetal DNA for genetic examination; 2. Detection time: usually performed after 16 weeks of gestation, and examination before 16 weeks may increase the risk of miscarriage, amniotic fluid leakage, and fetal malformation. If the pregnant woman has signs of miscarriage, signs of infection or coagulation dysfunction, etc., this test should not be performed. Chromosomal examination: 1. Basic principle: to detect the number and structure of chromosomes through blood, to clarify whether there are chromosomal abnormalities, which can be used to diagnose whether the fetus is developing normally. Chromosomal abnormalities are mainly manifested as increased chromosomes, and the fetus may have malformations and mental retardation; 2. Testing time: clinical examination is usually performed at 14-20 weeks.