Birth defect, congenital anomaly; structural or severe functional defect present at birth. Birth defects cause about 10% of neonatal deaths. A major anomaly is apparent at birth in 3–4% of newborns; by the age of 5, up to 7.5% of all children manifest a congenital defect. The incidence of specific congenital anomalies varies with a number of factors: (1) Individual defect (common malformations such as cleft lip and cleft palate occur in 1 in every 1,000 births). (2) Geographical area (because of factors such as differences in the genetic pool or the environment). For example, the occurrence of spina bifida is 3–4 in every 1,000 births in areas of Ireland, but under 2 in 1,000 in the United States. (3) Cultural practices: where marriages between relatives are frequent, the incidence of certain defects increases. (4) Certain prenatal problems. Scientists estimate that about 2.5–3% of infants born annually in the United States begin life with major birth defects; counting minor types of defects, the percentage increases to 7–10%.