Do you really want to know? According to a site purporting to have "heavy spoilers" and lots of leaked scenes...
Originally Posted by sediment
...she's a victim of spousal abuse (her hubby's signature hands-free force choke) from which she "never fully recovers," and then she "dies after giving birth to the twins." How long after? Immediately after, as in complications during child-birth? Or some time later? To die giving birth to Luke and Leia would indeed be the easiest way for Lucas to kill this character off. Almost a cop-out, I would say. However, I remember Leia telling Luke in Ep. 6 that her mother died when she was "very young," but that she had memories of her mother -- faces, images. Does birth count as "very young?" Would she have memories after several minutes of life? Perhaps a few years elapse over the course of the movie before we see what finally does Padme in. Or perhaps we never actually see her die and those scenes of her final hour are lost to the nether-region between the end of Ep. 3 and the beginning of Ep. 4. The leaked scences from the movie definitely show her on a hospital bed of some sort, but she is still alive. The person who posted the images says that Obi-Wan is saying farewell to her, but perhaps these are only scenes of the twins' birth and the narration was simply some misleading information. But then we're back to the question: How and why exactly does she die?
Sorry to babble on. I'm well aware that this is a Disney forum and that there are whole forums devoted to Star Wars and that everything's probably been very neatly solved over there, but hey. :o