It’s impossible. Lois could never have Superman’s baby. Do you think her fallopian tubes could handle the sperm? I guarantee you he blows a load like a shotgun right through her back. What about her womb? Do you think it’s strong enough to carry his child?…He’s an alien, for Christ’s sake. His Kryptonian biological makeup is enhanced by Earth’s yellow sun. If Lois gets a tan the kid could kick right through her stomach. Only someone like Wonder Woman has a strong enough uterus to carry his kid. The only way he could bang regular chicks is with a kryptonite condom. But that would kill him.
– Brodie from Mallrats
I think the only reason DC has finally decided to couple Superman and Wonder Woman in continuity (it’s happened plenty of times in Elseworlds tales) is they can finally show Superman as a sexual being. The only time I can recall that Superman had sex with Lois in the comics was during Brian Azzarello/Jim Lee’s brief “For Tomorrow” arc (at least it was implied. Who knows what really happened?). As silly as Brodie’s line was in Mallrats, every comic book geek has discussed the illogical nature of Superman and Lois having sex.
Now we can have tasteful superhero sex in the New 52 like Batman and Catwoman.