@Magic: I dunno... as a society we know a lot more about male genitalia than we do about female. The male orgasm has been explored inside and out, but you can't say quite so much about the female orgasm. Some doctors don't believe in the g-spot, some do, some believe it's just the back of the clitoris, some say that not all women can orgasm vaginally, some say that all of them can. So who's right? Nobody knows. It needs to be sorted out, really.
@Distorted Fairytale: a woman who has not has children is more likely to reject the IUD, and women who go on to have sex with multiple partners are more at risk of developing pelvic inflammatory disorder, which can result in infertility. As far as I know, those are the main reasons given. However, that doesn't mean it's totally impossible to get one put in. My sister is 22 and she got married six months, is childless and recently got the IUD. I don't know if it's different because we're in England.