Down’s Syndrome is common with older women ... not ones the age of her daughter.
Actual fact is:
Although Older women have a higher PERCENTAGE of Down Syndrome births, the majority of children with Down Syndrome (80%) are born to mothers under 35.
from March of Dimes website...
Does the risk of Down syndrome increase with the mother’s age? Yes. The risk of Down syndrome increases from about 1 in 1,250 at age 25, to 1 in 1,000 at age 30, 1 in 400 at age 35, 1 in 100 at age 40 and 1 in 30 at age 45 (6). Women over age 35 have been traditionally considered most likely to have a baby with Down syndrome. 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 (2).