defect

(dē′fekt″ )

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(di-fekt′ )
[L. defectus, weakness, failure]
A flaw or imperfection.
defective (di-fek′tiv )

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, adj.
Common Birth Defects

Type of Defect	Examples	Approximate Prevalence per 10,000 Births	Comments
Chromosomal	Down syndrome (trisomy 21)	13	Increases with maternal age over 35 years
	Trisomy 18	2.3
Infectious	Varicella-zoster infection (chickenpox)	7
Metabolic	Phenylketonuria (PKU)	3.5
Structural	Cleft lip and/or palate	10
	Neural tube defects, including anencephaly and spina bifida	3	Folate supplementation during pregnancy prevents neural tube defects
	Transposition of the great vessels	5
Toxic	Fetal alcohol spectrum disorders	2-15	Varies with prevalence of alcohol use in the community; preventable with abstinence
	Isotretinoin (acne medication)		Avoid all pregnancies during therapy with isotretinoin

Birth Defects by Categories, with Examples

Structural/Anatomical Defects	Examples
Craniofacial	Cleft lip or cleft palate; craniosynostosis
Heart and blood vessels	Aortic coarctation; hypoplastic left heart; patent ductus arteriosus; tetralogy of Fallot; transposition of the great vessels; ventricular septal defect
Limbs	Absent limbs or digits; conjoined limbs or digits; extra limbs or digits; malformations, e.g., club foot
Neural tube	Myelomeningocele; spina bifida; encephalocele
Chromosomal/genetic syndromes or microdeletions	Extra chromosomes, e.g., Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Klinefelter syndrome; sickle cell anemia
Digestive/Intestinal	gastroschisis; Hirschprung disease; pyloric stenosis
Excretory	Congenital hydronephrosis; renal agenesis or dysplasia; hypospadias; choanal atresia
Functional/Developmental Defects	Examples
Neurological/Psychiatric/Behavioral	Congenital hypothyroidism; fetal alcohol syndrome
Metabolic	Inborn errors of metabolism, e.g., homocystinuria, phenylketonuria
Degenerative	Lysosomal storage diseases; muscular dystrophies
Birth defects affecting special sense organs	For example, congenital deafness; congenital cataract

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