A heart murmur is a sound made by blood moving through the chambers and valves of the heart or through the blood vessels near the heart. The sounds can be heard through a stethoscope.

Heart murmurs are common in infants and children and are harmless in most cases. The murmurs usually are not a problem, require no treatment, and go away on their own. Pregnancy, fever, and some types of anemia can also lead to temporary heart murmurs. But some adults have harmless heart murmurs that do not go away.

A heart murmur may sometimes mean there is a more serious problem with the heart walls or heart valves, such as narrowing or leaking of a heart valve (stenosis or regurgitation) or an infection of a heart valve (endocarditis). These problems can cause blood to flow abnormally through the heart valves or chambers, causing a murmur or other sound that the doctor can hear with the stethoscope. These conditions require close monitoring and may require treatment.