Anyway I read something interesting that I wanted to share from the book:
This does not mean people have stopped having children- merely that in the Second Demographic Transition, procreation became an act of self-actualization. And because raising children is difficult, resource intensive, socially inhibiting, and (if can be candid) often unpleasant, it is not an exercise many people want to put themselves through multiple times.
What To Expect When No One's Expecting, pg 93
The second sentence is also quite interesting. Raising kids has always been time and resource intensive but in spite of all of our cultural noise about how important kids are we are at the same time doing everything we can to make raising kids more and more difficult.