The first part of the movie- starting with Bella's pregnancy- reminded me a little of the Vampire pregnancy storyline from S3 of Angel- there being a mystical Vampire pregnancy that the pregnant character is struggling to take to term because of incompatible physiology and there are a lot of outside players trying to destroy it, take it, or figure out how it happened.
Damn, I totally forgot about the Darla storyline in S3 of Angel. I'm a huge fan of that show. Yeah, vampires can get pregnancy in other fiction. I thought it was weird how some people found that so hard to believe.
The BD book is interesting. It was like the author somehow KNEW her movie was going to be made into two movies, so she had that that part with Bella opening her eyes as the cliffhanger. There is a ton of stuff in the second part of the movie. I don't think it will be too hard for them to make a movie about it at all.