The causes of congenital heart disease can be broadly divided into three aspects: genetic factors, environmental factors and disease and drug factors. Genetic factors: Take trisomy 21 as an example, about 50%; patients with this disease have congenital heart disease, among which endocardial cushion defect and ventricular septal defect account for 32% and 29% respectively, followed by atrial septal defect accounting for 11%, tetralogy of Fallot accounting for 7.9% and endarterectomy accounting for 6.7%;. Most of the simple atrial septal defects, ventricular septal defects, patent ductus arteriosus, and tetralogy of Fallot show a polygenic pattern, and the risk of reoccurrence in siblings and children of those with the first disease is around 4%. Environmental factors: refers to the environment of the pregnant woman before and during the pregnancy, including the living and working environment. Environmental factors include chemical and physical factors. Chemical factors: mainly long-term exposure to harmful chemicals, including benzene, sulfur dioxide and other harmful gases and heavy metals such as mercury and cadmium. Therefore, pregnant women should avoid living in newly renovated houses, as well as avoiding exposure to chemical factors and strengthening protection. Physical factors are mainly radiation, because radiation has pathogenic effect on human body and teratogenic effect on fetus. Disease and drug factors: According to some analyses from medical studies, drug and disease factors mainly include alcoholism of the mother, aspirin taken by the mother in early pregnancy, taking tetracyclines, taking birth control pills, rubella and cold. These are all high-risk factors for congenital heart disease in children. Therefore, mothers should try to avoid drugs and disable high-risk drugs during pregnancy, especially in early pregnancy. This should be the main measure for primary prevention of congenital heart disease. The mother should also avoid colds and bacterial and viral infections such as rubella and measles in early pregnancy, because bacterial and viral infections can also lead to malformations in fetal development and cause congenital heart disease. In addition, advanced maternal age is also a high risk factor for the development of congenital heart disease in the fetus. For genetic factors, parents who have a family history of genetic diseases should try to rule out the possibility of congenital heart disease in the fetus through chromosome examination and genetic gene examination during pregnancy; in addition, to prevent the occurrence of congenital heart disease pregnant women should avoid living in newly renovated houses, avoid exposure to chemical factors; avoid exposure to radioactive substances, avoid living in an environment with strong electromagnetic waves; try to avoid using drugs, prohibit high-risk drugs. What should a pregnant woman do if she has a cold or rubella? Bacterial and viral infections can cause malformations in fetal development and congenital heart disease. Therefore, pregnant women should also avoid colds and bacterial and viral infections such as rubella and measles. In case of colds and rubella and measles infections, they should promptly consult a professional doctor and not take medication indiscriminately.