Gene-Environment Interaction (Birth Defect Information)

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Genetic variations and environmental factors play key roles in the causes of birth defects.¹  Twenty percent of birth defects are caused by chromosomes inherited from parents.²  Children with birth defects may have too few or too many chromosomes, which then influences their structural development.³ 

Environmental factors such as infection, exposure to hazardous waste and drug use by mothers are associated with approximately 10 percent of birth defects.²  The occurrence of heart defects has been linked to infections such as rubella (German measles) and toxoplasmosis (a parasitic disease).¹ Cleft palate has been associated with radiation exposure during the first trimester of pregnancy.²

Although 70 percent of birth defects have an unknown causal factor, many birth defects are caused by a gene-environment interaction.  An unborn infant may carry  certain genes that would cause a birth defect in combination with harmful environmental factors.³ One example of gene-environment interaction was uncovered in a past study of smoking and oral clefts. A study conducted by CBDMP (PDF), combined interview data detailing mothers’ smoking habits with DNA testing to determine the infants’ status for a particular gene, transforming growth factor alpha (TGFA).  It was found that:

References

1. March of Dimes (2006). Quick reference and fact sheets: Birth defects. Retrieved on May 21, 2009, from http://www.marchofdimes.com/pnhec/4439_1206.asp
2. Cleveland Clinic (2005), Birth Defects. Retrieved on May 21, 2009, from http://my.clevelandclinic.org/disorders/Birth_Defects/hic_Birth_Defects.aspx
3. Mekdeci, B. & Schetter, T. (2003). Protecting our health: Birth defects and the environmental. Retrieved on May 21, 2009, from http://www.protectingourhealth.org/newscience/birthdefects/2004-0501birthdefectspreview.htm