Here's a link to an article. http://www.ivfnewsdirect.com/?p=350
This study, or at least this article about it, focuses on the fact that hysteroscopies seem to find uterine pathologies that were undetected in other kinds of testing. So even women whose doctors thought them to have no pathologies were found to have pathologies which, once corrected, led to successful implantation. The study is focused on women who have had repeated BFNs even though all the variables (egg quality, uterine lining, etc.) were thought to be in good shape. In short the hysteroscopies found things that other tests missed and this led to improved implantation/pregnancies for the subjects of the study.
There is an allusion to, but no stats about, what my doctor said about how, separate from correcting whatever the problem is, simply the act of irritating the lining improves the lining for implantation. He did clearly say that to me. And the doctors mentioned in the post below seem to have said the same thing to their patients. Perhaps there's another study out there that I didn't find in my quick Internet search yesterday. Or maybe it's in this study, but not reported on.
I'm inclined to trust my doctor on this, especially since my acu has had numerous patients who tried unsuccessfully for a long time even though there were no particular problems and once they had a hysteroscopy or D&C they conceived.