It's not known why atrial septal defects occur, but congenital heart defects appear to run in families and sometimes occur with other genetic problems, such as Down syndrome. If you have a heart defect, or you have a child with a heart defect, a genetic counselor can estimate the odds that any future children will have one.

When the following conditions occur during pregnancy, they can increase your risk of having a baby with a heart defect:

  • Rubella infection. Becoming infected with rubella (German measles) while pregnant can increase the risk of fetal heart defects.
  • Drug or alcohol use or exposure to certain substances. Use of certain medications, alcohol or drugs, such as cocaine, during pregnancy can harm the developing fetus.
Dec. 14, 2011