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Risk Factors for Chromosomal Abnormalities

A risk factor is something that raises your chances of getting a disease or health problem.
You can have a child with a chromosomal abnormality with or without the factors below. The more you have, the greater your chances will be. Talk to your doctor about how you can lower your risk.


The leading cause is the mother’s age. The chances get higher as the mother ages. The number of abnormalities passed on is hard to know because most do not end in live births.
Age Risk of Any Abnormality Risk of Downs Syndrome
15-24 1/500 1/1500
25-29 1/385 1/1100
35 1/178 1/350
40 1/63 1/100
45 1/18 1/25
These statistics only account for live births.


Your risk is higher if you have had a child with an abnormality in the past.
Talk to your doctor about testing if you and your partner have had at least two miscarriages. If the results are not normal, you and your partner should meet with a geneticist.

Living Environment

Urban air pollutants can harm babies in the womb. They can raise your chance of having a child with abnormalities.


Chromosome abnormalities. National Human Genome Research Institute website. Available at: Updated January 6, 2016. Accessed July 30, 2018.
Study: prenatal exposure to air pollutants causes genetic alterations. Columbia University website. Available at: Published February 22, 2005. Accessed July 30, 2018.

Revision Information

  • Reviewer: EBSCO Medical Review Board Kathleen A. Barry, MD
  • Review Date: 05/2018
  • Update Date: 07/30/2018
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