How congenital heart disease is caused, the cause is not exact, the possible reasons are as follows: 1, the mother during pregnancy disease, especially the disease toxic diseases, such as colds, rubella and other cases, is likely to cause the occurrence of congenital heart disease; 2, women use drugs during pregnancy, for example, in early pregnancy do not know that they are pregnant, due to a disease began to use drugs, some drugs are likely to have a teratogenic effect; 3, genetic, the Some families have this type of genetic inheritance. The most common causes are the above three conditions, but the above three conditions do not necessarily lead to congenital heart disease, and now the causes of congenital heart disease, including ventricular septal defect, are not exact.