Congenital heart disease (congenital heart defect) is one or more abnormalities in your heart’s structure that you’re born with.  This most common of birth defects can alter the way blood flows through your heart.  Defects range from simple, which might cause no problems, to complex, which can cause life-threatening complications. Advances in diagnosis and treatment mean most babies who once died of congenital heart disease survive well into adulthood.  However, signs and symptoms of the condition can occur in adults later in life, even those who had treatment as a child.