Here is some info on a woman’s fertility with age. This is literally the chance per month (menstrual cycle) that a woman is likely to get pregnant if she has sex.
As we can see, it is at its highest around age 20-22 (info on teen years seems to be stable at the highest levels), and then falls off. After about age 37, it collapses.
Chance of miscarriage:
Chance of infertility:
In practical terms, I think of a woman’s prime childbearing years as around age 18-25, a secondary but still high plateau around age 26-32, a quick decline during 33-40 and a few wisps and vapors after 40. Thus, if we are to follow Natural Law, we should aim for women to get married and have children around 18-25, with her last children perhaps coming around age 32. From this it follows that there is not really much need for college and working.