Prenatal diagnosis is also called “prenatal diagnosis” or “intrauterine diagnosis”. On the basis of genetic counseling, it is the application of various advanced scientific and technological means, such as imaging, biochemistry, cytogenetics and molecular biology, to understand the developmental status of the fetus in utero and to diagnose congenital and genetic diseases before the birth of the fetus. It is the wish of every family to have a healthy child. However, about 200,000 to 300,000 children with congenital malformations visible to the naked eye are born in China every year. Together with the defects that become apparent only months and years after birth, the total number of children with congenital disabilities is as high as 800,000 to 1.2 million, accounting for about 4% to 6% of the total number of births each year. The direct economic loss caused by neural tube abnormalities in China is more than 200 million yuan every year, the treatment cost of congenital stupidity is more than 2 billion yuan, and the treatment cost of congenital heart disease is up to 12 billion yuan. Therefore, the current situation of birth defects in China is not only a serious public health problem, but has become a social problem that affects the economic development and normal life of people in China. Prenatal diagnosis is an important medical procedure to help couples who need prenatal diagnosis to have a healthy baby through selective abortion of the affected fetus, and is also an important line of defense to improve the quality of our birth population and reduce birth defects and disabilities. Prenatal diagnosis is aimed at the following diseases: 1) diseases with clear diagnostic criteria and accurate and reliable prenatal diagnosis methods; 2) diseases with serious symptoms that cause stillbirth, stillbirth or disability; 3) diseases without effective treatment; 4) diseases with high genetic risk. Types of prenatal diagnosis: 1. chromosomal diseases; 2. sex-linked genetic diseases; 3. inborn metabolic defects; 4. non-chromosomal congenital anomalies. Indications for prenatal diagnosis: 1. Pregnant women aged 35 years or above (or husbands aged 40 years or above); 2. Pregnant women with positive serum screening in the early and middle stages of pregnancy; 3. Pregnant women with chromosomal disorders in one of the spouses or those who have had pregnancies or children with chromosomal disorders; 4. Pregnant women with a history of unexplained spontaneous miscarriage, malformation, stillbirth or stillbirth; 5. Abnormalities found in ultrasound examinations (such as excessive amniotic fluid 6. fetuses with suspected intrauterine infections (e.g. toxoplasmosis, cytomegalovirus, rubella virus, herpes simplex virus infection, etc.); 7. fetuses with edema or anemia or both couples are carriers of thalassemia; 8. couples with a history of exposure to teratogenic substances; 9. fetuses with mental retardation; 10. fetuses with severe single gene Pregnant women who are at high risk of conceiving a fetus with a severe monogenic genetic disease; 11. Pregnant women who have a congenital neural tube defect, or who have conceived or given birth to a child with this disease; 12. Pregnant women with a family history of hereditary diseases; 13. Pregnant women who have a congenital metabolic disease or have given birth to a child with this disease; 14. Pregnant women with fetal growth retardation.