ive been saying for years now that one of the major plot points in this is going to be dooku holding padme prisoner, and anakin having to make a choice between serving seeing her die, or killing dooku and taking his place at the emporers right hand (in a rather bizarre future-echo of return of the jedi) - ive a funny feeling that the revalation that she is pregnant is what pushes anakin over the edge.
just a pity that no-one bothers to point out that its twins shes having...
oh - and one small point - if vader was looking for his son for all these years - why didnt he go and check on his family on tattoine?? surely that would have been the most logical place to hide him??