Down Syndrome

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…have a baby with Down Syndrome, mothers or fathers who have a rearrangement involving chromosome 21, and mothers over 35 years of age are at greatest risk. The risk of Down Syndrome increases with age, from about 1 in 1,250 for women at age 25, to 1 in 1,000 at age 30, I in 400 at age 35 and 1 in 100 at age 40. However, about 80 percent of babies with Down syndrome are born to women who are under age 35, as younger women have far more babies.