One out of every 100 infants born in the United States has a congenital (present at birth) heart defect -- a problem that occurred as the baby’s heart was developing during pregnancy, before the baby is born. Congenital heart defects are the most commonly occurring birth defect.
A baby's heart begins to develop at conception, but is completely formed by eight weeks into the pregnancy. Congenital heart defects happen during these crucial first eight weeks of the baby’s development. Specific steps must take place in order for the heart to form correctly.
Often, congenital heart defects are a result of one of these crucial steps not happening at the right time, leaving a hole where a dividing wall should have formed, or a single blood vessel where two ought to be.