In my opinion, Padme was so traumatized by Anakin´s turn to the dark side, she didn´t feel like living anymore.
I was most disappointed in Padme for choosing to pass away in the manner she did. I believe she should have decided to live and opposed Vader. If Padme was as devoted to her ideals as we had seen, she shouldn´t have broken so easily. So many possibilities, cinematic and literary died with her.
Originally Posted by DarthMaphisto86
Even though it is not that big of a deal to me how Padme died, in one of the most recent Star Wars novels called Corucant Nights II: Streets of Shadows, Padme's cause of death was apparently a fractured hyoid bone among other things caused by Anakin's Force choke. Obviously the droids on Polis Massa did not know the cause of death because there was no visible signs of trauma and the truth was only revealed in a secret autopsy before the late senator's funeral.
This truth is too simplistic to be the real one. Surely the medical droids wouldn´t have been so inefficient as to not perform a full physical examination of Padme. The author of the novel did not understand how Padme could have died because of a more complex reason.