If a woman begins to have children during her fertile years, she can usually continue to have children well into her 40's. (As long as she's otherwise healthy.)
If she waits until later to *begin* having children, fertility is dramatically reduced.
Personally, I think that it's a the hormonal contraception that's required to postpone childbirth for decades that screws us up.
Yes...that’s what I tried to say, but you said it better.