The etiology of congenital heart disease is still unclear, and the four possible related causes include genetic factors, environmental factors, drugs, and disease factors. Genetic factors: Take trisomy 21 as an example, about 50% of patients with this disease are accompanied by congenital heart disease. Most of the cases of pure atrial septal defect, ventricular septal defect, ductus arteriosus, and tetralogy of Fallot show polygenic inheritance pattern, and it is quite common for siblings to have the disease at the same time, and for parents and children to have the disease at the same time, and the nature of the disease is very similar. Environmental factors: refers to the environment in which the pregnant woman is exposed to before and during pregnancy, including chemical and physical factors. Chemical factors are mainly the long-term exposure of pregnant women to harmful chemicals, including benzene, sulfur dioxide and other harmful gases and heavy metals such as mercury and cadmium. Physical factors are mainly radiation, and excessive exposure to radioactive substances such as X-rays and isotopes in early pregnancy can easily cause fetal cardiovascular malformations. Drug factors: Exposure to teratogenic drugs such as lithium, sodium phenytoin or steroids in early pregnancy can lead to an increase in fetal morbidity. The use of aspirin, tetracyclines, birth control pills, sympathomimetic and amphetamine-like drugs, alcohol consumption, and marijuana use in early pregnancy have also been reported to cause the disease. Disease factors: Pregnant women with untreated and uncontrolled diabetes mellitus may have a substantially increased risk of congenital ventricular septal defect in the fetus. The fetus is susceptible to the disease if the woman is infected with a viral infection, such as a cold or rubella virus, during the first trimester of pregnancy. Since all of these reasons are high-risk factors for congenital heart disease in children, mothers should try to avoid them during pregnancy.