Defects present at birth, resulting from hereditary factors, environmental influences, or maternal illness.

Birth or congenital defects are present at birth and result from hereditary factors, environmental influences, or maternal illness. Such defects range from very minor, such as a dark spot or birthmark that may appear anywhere on the infant's body, to more serious conditions that may result in marked disfigurement or limit the lifespan of the child. A number of factors individually or in combination may cause birth defects. Heredity plays a major role in passing birth defects from one generation to the next. Such conditions as sickle-cell anemia, color blindness, deafness, and extra digits on the hands or feet are hereditary. The condition may not appear in every generation, but the defective gene is usually passed on.

Low birth weight is the most common birth defect, with one in every 15 babies being born...