Question: Its was proven that Down Syndrome affects children born of older women, but why is it that nowadays, younger women produce children with extra chromosome, that's Down Syndrome?

Remsha Afzal answered on 16 Nov 2018:

That is simply because older mothers tend to have fewer babies. 🙂 But in general older women DO have a higher chance of having babies with downs syndrome than younger mothers but we don’t notice it because fewer ladies become mothers over 40.
The chance that a woman under age 30 who becomes pregnant will have a baby with Down syndrome is less than one in 1,000, but the chance increases to 1 in 400 for women who become pregnant at age 35. By age 42, the chance is one in 60 that a pregnant woman will have a baby with DS, and by age 49, the chance is one in 12!