Baby atrial septal defect is a defect between the left and right atria at birth, resulting in the mixing of blood at the atrial level, which may be related to the following: first, genetic mutation, genetic mutation is a common cause of atrial septal defect, genetic mutation causes the baby’s heart to be stunted and atrial septal defect; second, when the baby is in the mother’s body, the mother is exposed to rays, hair dye, etc. in early pregnancy or early pregnancy Second, when the baby is in the mother’s body, the mother is exposed to radiation, hair dye, etc. in early pregnancy, or early pregnancy, unbalanced diet, fatigue, cold, or oral intake of some drugs that may have an effect on the baby, there may be organ development disorders, heart malformation, and atrial septal defect; third, the baby’s atrial septal defect may also be caused by the mother’s late pregnancy, because of multiple pregnancy, overdue pregnancy, and low amniotic fluid. So there are many causes of ventricular septal defect in babies, but in general genetic defects are the main cause.