An abnormality of structure, function, or metabolism (body chemistry) present at birth that results in physical or mental disability, or is fatal. Currently, birth defects rank as the leading cause of death for infants during the first year of life.
Congenital Anomalies, Chap. 14 in International Classification of Diseases Version 9 manual (740-759)
conditions resulting from faulty prenatal development. Structural birth defects—those affecting the body—are usually apparent in the first year of life. Functional problems in brain development (leading to learning problems or mental retardation) may not be apparent until childhood.