A '''birth defect''' is a structural, functional, or metabolic abnormality present at birth that results in physical or mental disability or death. There are more than 4,000 known birth defects, which may be caused by [[gene|genetic]] or [[environment|environmental]] factors. About 150,000 babies are born each year with birth defects. | A '''birth defect''' is a structural, functional, or metabolic abnormality present at birth that results in physical or mental disability or death. There are more than 4,000 known birth defects, which may be caused by [[gene|genetic]] or [[environment|environmental]] factors. About 150,000 babies are born each year with birth defects. |