A birth defect is an abnormality of structure, function or metabolism (body chemistry) present at birth that results in physical or mental disabilities or death. Although t he cause of most birth defects, the good news is that are ways to prevent some birth defects.

There are three main categories of genetic birth defects:

• Single-gene defects: A mutation (change) in a single gene can cause birth defects.
• Chromosomal birth defects: Abnormalities in the number or structure of chromosomes can cause many birth defects. Chromosomal abnormalities usually are caused by an error that occurred when an egg or sperm cell was developing.
• Multifactorial birth defects: Some birth defects appear to be caused by a combination of genes and environmental exposures.

January 2010
Sources: HealthDay and Healthwise

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