Causes: It is generally believed that early pregnancy (5-8 weeks) is the most important period for fetal heart development. There are many reasons for the development of congenital heart disease, genetic factors only account for about 8%, while the majority of 92% are caused by environmental factors, such as women taking drugs during pregnancy, infection with viruses, environmental pollution, radiation, etc. can cause abnormal fetal heart development. In particular, rubella virus infection in the first three months of pregnancy can sharply increase the risk of congenital heart disease in children.