In
Together again by Chiara Prato ( btw a great story!
) Lois thinks her baby is Lex's when he's Clark's, probably because a shorter gestation period, but I don't remember the
six months period thing; I don't know if you're searching for this story...
ED: found it! In "Together again" she says:
he was only born six months after... he was only born six months after... after that night...
I love this story!
Simona