Er... date rape?
I'm surprised no one mentioned it yet - that the little girl basically seems to have been conceived during a date rape of a completely drunk woman/ former man, who even told Walter she/ he couldn't sleep with him and felt rightly violated the next morning.
It kind of ruined the "fun" for me - will daddy ever tell his little girl? "I impregnated mom when mommy was passed out from drinking with me, it was the only time we ever slept together, and then she died givin birth to you?"
Cue the "It's a comedy, it was fun, no one takes this *beep* serious!" - calls.
After all, tis was a movie were someone was murdered and we're supposed to find it funny. But the thing is - murder doesn't happen because people aren't correctly identifying it as murder or at leas manslaughter while they're doing it - or playing it down. Besides that, I don't know anybody who has been killed by their three mistreated ex girlfriends. I know plenty of aussault vivtims, and be aware or not, so do you.
Sexual violence does happen because many date rapists tell themselves drunk people are fair game, or it hasn't been really rape - because the victim slept with them before, went home with them, is a slut or whatever, and play it down. Maybe that's why it comes across differently when it's "supposed to be funny".
Also, it's lazy writing - they had this cop out idea with a female baby, and didn't know any other plausible way to make him/ her give birth to one. Not creative.