When I was in college, several decades (!) ago, I remember an economics professor saying that with the migration from farms to cities, children went from being assets to liabilities. He said people used to have lots of children because they needed lots of help running farms, and feeding them wasn't an issue because they grew their own food, so each child eased the burden on the parents. But in the city, dad (or later, dad and mom) had to work to buy food, clothing, and all other needs for the kids, so each new kid added to the burden, at least until he was old enough to get a job and contribute financially.
This doesn't touch on the subject of blessings or spirituality, it just helps to explain the shift in attitudes to a general feeling that very large families are not as desirable from a purely economic standpoint. Unless you give birth to the Osmond family, of course.