Amniocentesis is the extraction of amniotic fluid by puncture of the amniotic cavity. After the amniotic fluid is extracted, a cell culture is performed to check the chromosomes of the fetus to see if there are any chromosomal abnormalities in the fetus. This method is widely used and less invasive, and the technology is more mature. This method is the most commonly used method for interventional prenatal diagnosis. Generally, amniocentesis is used to extract amniotic fluid during the 18-24 weeks of pregnancy. If it is too early, there will be fewer fetal cells in the amniotic fluid and the culture may be unsuccessful. If the amniotic fluid is taken at too early a stage, the fetal chromosomal abnormality will be induced and the mother will be harmed, so the amniotic fluid test should be done at 18-24 weeks of pregnancy. Further interventional prenatal diagnosis is needed if there are fetal ultrasound abnormalities, high risk of Down’s syndrome screening, previous adverse maternal history, or advanced age during prenatal checkups.