[bryanlarsen]

Talk to upper middle class people that have 4 or more children. They'll likely tell you that life gets easier after the 4th and subsequent children. I've heard of fathers describe it as switching from "man-to-man defence" to "zone defence". Your experience and parenting skills no longer have to be learned. Older children help with care for the younger. And not inconsequentially, your expectations rationalize.

My wife wanted more than our 2 children, but medical reasons prevented us from having more.

Most of my children's friends are in 2 child families. IMO middle class people tend to stop at 2 for financial reasons. OTOH, we know several couples who are both surgeons or in similar occupations. They tend to have either 0 or 4+ children.