It sounds pretty, but I have a hard time believing that women on either side of the aisle would be completely forthright, enough to create a statistically accurate study. How do you know if women who say they have NOT had an abortion - for the sake of the other study group - are actually telling the truth? What will they say when recruiting women for the study? Apply only if you can be honest? And that's not how statistics are gathered usually anyway, right - how often are formal study groups used as opposed to clinical information gathered from non-human sources like records? I'd like to think it could be done, but I'm not convinced.
I don't think at this point it is a matter of being able to draw a link or not. The suspicion is valid, based on what I've read, and proving the link is still in its beginning stages. Besides that, there's considerable opposition to these studies and their implications. It'll take time either way, and dismissing it out of hand is unwise, imo.
Wouldn't an abortion be in a woman's medical record? Were these studies completed via 'survey' or were they completed with the help of doctors counting incidents? If a survey, then yes, the results could be suspect to some degree, but the same would go for those whose studies claim there is no link.