nah, that's just a hag myth. it gets harder to get a woman pregnant as a man gets older, but the rate of mutants doesn't increase much. that's women. there are no problems with a 70 year old man having children, other than that he won't be able to take care of his kids.  so you shouldn't get them later than your 50s probably. i'd say 60 is the cutoff for men, and 35 for women.
Norway