I think it has been pretty standard throughout history for less educated/skilled people to have more children, although now the problem is that since both parents of the family are skilled and working full time, they have much less time to raise a significant number of children.
It's been standard in the last fifty years because of contraceptives and education about how to use contraceptives. But before contraceptives, I don't see why a skew would emerge. I read that in the Jewish community a long time ago it was the rabbis that had the most kids only because they could afford to raise them.
"Before contraceptives" isn't really a thing, we have evidence of contraception methods being used from 1850BC...
Check and check, now all we need is the “Idiocracy was a documentary“ comment to complete the “well, I can’t come right out and say that I think eugenics makes sense” veiled discussion. I’m sure all the people that agree with you are lockstep in thoughts an ideology with their parents, right?