Fetal cells are obtained through amniocentesis or chorionic villus puncture or cord blood puncture for cell culture and chromosomal karyotyping, of which amniocentesis is the most widely used. Advantages: 1, can detect all chromosome number abnormalities and large segments of chromosome structural abnormalities; 2, is currently the “gold standard” for prenatal diagnosis of fetal chromosomal disorders. Limitations: 1, in general, puncture is relatively safe, but there are still individual puncture failure, causing miscarriage, infection, amniotic fluid leakage risk, amniocentesis of the overall fetal loss rate of about 0.5%; 2, there are individual differences in cell culture, can not ensure 100% success; 3, chromosome testing for chromosomal micro-structural changes, monogenic genetic diseases, polygenic genetic diseases, environmental and drug-induced intrauterine developmental anomalies. 3. Chromosome testing cannot completely exclude intrauterine developmental abnormalities caused by small chromosomal structural changes, monogenic genetic diseases, polygenic genetic diseases, environmental and drug-induced abnormalities, low proportional chimerism and maternal contamination. Indications Maternal age ≥35 years; prenatal screening suggests a high risk of fetal chromosomal abnormalities; previous history of adverse maternal history of fetal chromosomal abnormalities; prenatal examination of pregnant women suspected of fetal chromosomal disorders; one of the spouses is a carrier of chromosomal abnormalities; pregnant women may be a carrier of a certain X-linked genetic disease gene; previous history of adverse maternal history or exposure to specific teratogens. In recent years, it has been advocated that ICSI (intracytoplasmic sperm injection) should also be included in the indication for amniocentesis. Early Down has a higher detection rate than intermediate Down; ●Non-invasive has a higher detection rate than Down screening; ●Amniocentesis has the highest detection rate; ●Screening for low risk does not mean there is no risk; ●Screening for high-risk amniocentesis results in a majority of normal results; ●Down screening not only detects abnormalities of trisomy 21, trisomy 18, and trisomy 13, but also detects some sex chromosome and chromosome structural abnormalities, as well as neural tube defects; ●Non-invasive Positive screening still requires amniocentesis; ● Screening is risk-free and amniocentesis has a low, manageable, and acceptable risk.