MistaG: they shouldn't have, cos if you're on the pill you don't have a menstrual cycle. The pill works by making the body think that it's already pregnant, so no egg is released. So I don't think it's possible to have those symptoms whilst on the pill. Unless they're just bitchy and nervous and annoying by nature, and I know a few girls who are.
Re: childbirth. Apparently the cause of the pain is that humans walk upright, and this has (over eons) caused the birth canal to become misplaced within the body. Monekys don't have such trouble. Neither do cats, I've seen that with my own eyes.