Oh, man, that is a FANTASTIC question. I have no idea.
On average, as of 2016, 26.3 years for mothers, 31 for fathers.
https://www.nytimes.com/interactive/2018/08/04/upshot/up-birth-age-gap.html
Without a college degree - 23.8
With a college degree or higher - 30.3
I hesitate to share this, because it’s a little depressing, funny, but depressing.
John Oliver on school lunches (NSFW):
https://youtu.be/-YypArYDcjA