The overall risk of having a baby with a chromosome abnormality is small. But as a woman ages, the risk of having a baby with missing, damaged, or extra chromosomes increases. Down syndrome is the most common chromosome problem that occurs with later childbearing. The risk of having a baby with Down syndrome is

  • 1 in 1,480 at age 20 years
  • 1 in 940 at age 30 years
  • 1 in 353 at age 35 years
  • 1 in 85 at age 40 years
  • 1 in 35 at age 45 years
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