I agree with Bob; Lois definitely would have been pregnant in the 5th season (if there was one)... after all, wasn't Teri Hatcher pregnant in real life?
Yes, she was. But I don't think the plan was ever to have a pregnancy on the show. Indeed, according to Tim Minear, S5 was intended to start with the baby from FH having a rapid growth surge to instant teen and Lois and Clark having to deal with the problems of superteenage hormones and other teen problems amplified by super powers.
You might note that TM revisited that plotline with Angel (and almost killed off my interest in that show when he did. I loathed Connor.
).
Two other plotlines sketched in for the season were an episode in which LNC would be sent back in time and meet their teen selves and an episode in which Alt-Clark would find and be reunited with his Lois.
LabRat
