Lanefan
Victoria Rules
I already had to worry about this when DMing a pregnant Druid-equivalent with wildshape.Sure, if you're going for a 'consequences' game, though I suspect anyone who's actually running sexytimes with a pregnancy risk probably is.
EDIT: that would be an interesting extra level of rules to apply to the various polymorph spells and wildshape as well.
What I ended up doing was deciding that it'd work fine up to a certain point in the pregnancy (halfway? I forget now) after which she pretty much couldn't do it without losing the fetus.
Ironically enough, given the theme of this thread, this same character also had gender-swap issues. She started out as female, got turned to male by a wild magic effect applying a curse but was able to get herself turned back to female - temporarily - via Remove Curse. Problem was, every time she shapeshifted she'd flip back to male...until she got pregnant, which forced her to stay female until giving birth...after which she almost immediately flipped to male again. She has since been able to get the curse permamently removed.
Lan-"for anybody who might thinks I've never had to give this stuff any serious thought..."-efan