I'm not even going to begin thinking about having kids until at least after grad school.
Even then, chances are, we're going to adopt. Unless she's absolutely dying to go through childbirth, which I know she's not, we'd much rather help an orphaned child than contribute to the world's population. Besides, I don't want to be held responsible if the kid is ugly.
Seriously, though. That's not as much when you consider it's over a period of many years. It just looks bad because it's been clumped into some huge number. Like BOR said, "you manage," if this weren't managable, it wouldn't be happening.