I. What is amniocentesis? Amniocentesis refers to the use of a very fine puncture needle to enter the amniotic cavity through the abdominal wall and uterus of a pregnant woman under ultrasound positioning and surveillance, and to extract 20-30 ml of amniotic fluid specimens for tests such as thalassemia, karyotype and various hereditary monogenic diseases, usually performed at 18-24 weeks of gestation. Amniocentesis has been used in prenatal diagnosis for more than 30 years, and its accuracy and safety are the highest. What kind of people need amniocentesis? 1.Advanced age (over 35 years old) 2.Pregnant women with high risk of Down syndrome screening during pregnancy 3.Pregnant women with both spouses being carriers of the same type of thalassemia 4.Ultrasound suggesting fetal structural abnormalities 5.Pregnant women with one spouse being a balanced ectopic carrier of chromosomes 6.Family with known or suspected genetic diseases 7.Fetus with high risk of chromosomal abnormalities 8.Pregnant women with suspected high risk of intrauterine Pregnant women who are suspected of having a high risk of intrauterine infection. 9. Pregnant women whose fetus is considered to be at risk for abnormalities by the obstetrician based on clinical assessment. 10. In addition to chromosomal examination, amniotic fluid can also check the genes of thalassemia, hemophilia, polycystic kidney, Duchenne muscular dystrophy (DMD) and other genes according to the needs of different genetic diseases, and can also perform paternity test. For pregnant women with suspected fetal structural abnormalities or multiple ultrasound soft indicators abnormalities, fetal growth restriction, having a child with mental retardation, cerebral palsy or mental retardation, fetal chromosome and gene chip (array-CGH) examination is recommended, which can detect chromosomal microdeletions, microduplication syndrome, more accurate diagnosis of fetal abnormalities and assessment of prognosis.