I have to disagree a little with your first point — I don't not have children because I've made some factual calculation about it: I just don't want children. End of. My biological clock must have died in the womb.

I dislike the implication that everyone who is childfree must have made a difficult but rational decision, because it feeds into the theory that every woman should want children, and if we don't have them it's only because we're fighting against our impulses. It's just never been true for me or any of my friends.