What is a Congenital Heart Defect (CHD)? CHD is diagnosed when a child is born with an abnormally structured heart and / or large vessels. Such hearts may have incomplete or missing parts, may be put together the wrong way, may have holes between chamber partitions or may have narrow or leaky valves or narrow vessels. There are many types of congenital heart defects, ranging from those that pose relatively small threat to the health of the child to those that require immediate surgery. CHD Awareness Month is February.