Oh, wow, I hadn't even thought of the possibility of the baby being Clark's! I just assume the headaches were a fakeout so we wouldn't at first be thinking pregnancy. (I can't decide if I'm happy or not to have been spoiled by the pregnancy--I'm probably glad to have been able to be with the shock in advance, but it might have been fun to wonder if Lana was actually dying).

You make a good argument about that opening Lexana scene--if he *did* tell her to pick a charity to support and then got all controlling, that makes more sense to me that she would feel upset. (And honestly, her distress about the pregnancy *after* that conversation made a lot of sense to me--though I wasn't thrilled that her immediate reaction was to not want to hear anything bad about Lex, because that bodes very ill if she does stay in the relationship with him).

I also like your explanation about not wanting Lex to know until she's made a decision, but unfortunately I do think that given the politics of the show, abortion is unlikely to even be considered.
(Apparently birth control is even too radical for this show!)