I don't think Cordy was always pregnant, but AtS did rely on pregnancy as a plot device quite often, especially when you consider that no one on Buffy ever got pregnant. On AtS, Cordy got pregnant in season 1, then Darla became pregnant in season 2 and delivered in season 3, and then Cordy became pregnant again in season 4. A lot of the plot on AtS was driven by pregnancy. I'm a soap fan, so I'm rather used to that, but it was rather odd that a show featuring an undead main character involved so much sexual reproduction (versus the vampy, blood sucking thing).
You know, I was actually really surprised that no one on BtVS even so much as had a pregnancy scare. Every woman I know has had at least one false alarm. I think it would have been sort of neat to do a demonic twist on that... like maybe with Anya or something, what with her being newly human and all. I don't know. It's not a fully formed idea in my head, yet. I like that the BtVS characters had full lives and were more than just baby vessels, but I do think that for such a feminist show, it is strangely silent on reproductive issues. There's so much more than just the unwanted pregnancy angle to explore! What about wanted pregnancy? What about various reproductive diseases or disorders? What about having one of the women actually seem to have a period every once in awhile? I mean, hello... does cramp immunity come with the slayer package or something? In the long run, I think I would have liked to have seen less pregnancy on Angel and maybe a reproduction-related line every once in awhile on Buffy.