Like the sonar used by submarines to locate objects on the ocean floor, sound wave "echoes" are being used to diagnose congenital heart disease in infants while still in the uterus.

Fetal echocardiography is a painless and risk-free procedure that can be used as early as the 16th week of pregnancy.The use of echocardiography involves directing sound waves at the fetus's heart, recording the echoes, then converting those echoes into an image on a video screen to visualize the heart valves and chambers.

Dr. Deborah Friedman, a pediatric cardiologist at New York University Medical Center, said early detection of heart problems can save infants' lives. "When echocardiography indicates structural damage, we can be prepared for cardiovascular surgery, once the baby is born, to correct defects."