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Birth Defects

Causes of Birth Defects

There are many reasons why birth defects may occur. Sometimes the causes are genetic, sometimes environmental, and in many cases the causes of birth defects are unknown. Birth defects are found in babies all over the world, and while most babies are born healthy—97 out of 100, in fact—a small percentage are not.

Below are some potential causes of birth defects:

  • Genetic problems (i.e., one or more genes does not work properly or part of a gene is missing)
  • Chromosomal abnormalities, such as having an extra chromosome or missing a part of a chromosome
  • Single-gene defects
  • Multifactorial inheritance (i.e., when genetic and environmental factors are involved)
  • Teratogens (agents, usually in the environment, that cause birth defects, such as drug or alcohol use)
  • Environmental factors, such as exposure to German measles or rubella during pregnancy

Risk factors for birth defects include:

  • Taking drugs, smoking or drinking alcohol while pregnant
  • Having certain medical conditions, such as uncontrolled diabetes or obesity before or during pregnancy
  • Taking certain medications known to cause birth defects, such as isotrenin, a drug used to treat acne
  • Having a family member with a birth defect
  • The mother being over the age of 35

Locations for Birth Defects