Moo, I haven't replied to this topic yet...but perhaps you've read my mind.
I also feel a surrogate mother should have the right to abort, regardless of what wanna-mom and wanna-dad want. It's the surrogate mother's body, not the biological mother's, and if the surrogate suddenly has an issue with the arrangement, then too bleedin' bad for the parents because it's not her body. But, a lot of thought needs to go into the decision to let people use your body as an incubator. But...if we make it illegal for one group of women (albeit very small) to get abortions, this may very well open the door for the banning of abortions for other groups of women. We really should not put ideas into the heads of the pro-lifers.
Yeah, it would suck if the surrogate backed out and aborted, but perhaps the parents who bought her could demand a refund from her if it was that big of a blasted deal. Or...maybe the wannabe parents could accept the blasted fact that, if they can't conceive naturally, they aren't meant to spawn and should move on with their lives and donate that $6000 to children's charities instead of being selfish and bringing yet another kid into the world.
Let me pose another question based on the one the OP asked...what if the child the surrogate was carrying had some kind of defect (Down's syndrome, enecephaly (spelling?), missing organs, deformities, etc.)? What if she wanted to abort, but the parents using her body did not want her to? Or vice versa? What if the biological parents want to abort and the surrogate wants to carry to term?