Down Syndrome And Maternal Age
Researchers have established that the likelihood that
a reproductive cell will contain an extra copy of chromosome 21 increases
dramatically as a woman ages. Therefore, an older mother is more likely
than a younger mother to have a baby with Down syndrome. However, of
the total population, older mothers have fewer babies; about 75% of
babies with Down syndrome are born to younger women because more younger
women than older women have babies. Only about nine percent of total
pregnancies occur in women 35 years or older each year, but about 25%
of babies with Down syndrome are born to women in this age group.
The incidence of Down syndrome rises with increasing
maternal age. Many specialists recommend that women who become pregnant
at age 35 or older undergo prenatal testing for Down syndrome. The likelihood
that a woman under 30 who becomes pregnant will have a baby with Down
syndrome is less than 1 in 1,000, but the chance of having a baby with
Down syndrome increases to 1 in 400 for women who become pregnant at
age 35. The likelihood of Down syndrome continues to increase as a woman
ages, so that by age 42, the chance is 1 in 60 that a pregnant woman
will have a baby with Down syndrome, and by age 49, the chance is 1
in 12. But using maternal age alone will not detect over 75% of pregnancies
that will result in Down syndrome.
reproduced from the NIH National Institute of Child
Health & Human Development
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