Some congenital heart defects are diagnosed intrauterine, while others you may not know about for the rest of your life. Although the news of a child's heart defect most often falls on parents like a bolt from the blue, it is not always something to be feared. Fortunately, the most common defects that occur in children are generally harmless and resolve spontaneously. However, there are others that are much more serious and may require long-term treatment or surgical intervention.