Birth defects structural malformations

An estimated eight million children — about 6% of total births worldwide — are born with major birth defects annually. Additional 

A birth defect, a synonym for the clinical term congenital anomaly , is defined as an anatomical and/or functional defect resulting from disturbance of normal developmental processes. This definition includes a wide range of defects, from a visualized structural defect such as spina bifida to microscopic and metabolic defects such as phenylketonuria. Terms such as malformation, disruption, deformation, and sequence have been utilized to describe various manifestations (Jones, 1988). 

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The animal database provides strong evidence that developmental toxicity is a sensitive end point following 2,3,7,8-TCDD exposure. Structural malformations, functional alterations (including impaired development of reproductive system), decreased growth, and fetal/newbom mortality have been observed in several animal species. Limited human data on the developmental toxicity of CDDs is available. Most of these studies examined the occurrence of birth defects in children of males exposed to 2,3,7,8-TCDD. Deficiencies in the human data preclude drawing firm conclusion on the potential of 2,3,7,8-TCDD to induce developmental effects in humans. However, the animal data suggest that 2,3,7,8-TCDD is a likely human developmental toxicant. 

Figure 9 Pie chart of the relative percentages of the causes of human birth defects. It has been estimated by various authorities that cytogenetics contributes to no more than 5% of all malformed live births, Mendelian inheritance to no more than 15-20%, maternal infections 3% or 4%, maternal disease 3% or 4%, problems of constraint in utero (amniotic bands) 2%, and all drugs, chemicals, and radiation no more than 1% of the total load of structural birth defects in human beings.

Congenital heart defects are the most common form of birth defect occurring in infants. CHDs include a variety of structural malformations of the heart and its major blood vessels, resulting from abnormal embryonic development . CHDs affect the normal flow of blood through the heart. The exact etiology of CHD is unknown, but it is considered to occur as a result... 

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