What's also interesting is that side-effects of the Back to Sleep campaign. I've noticed a rather large increase in corrective helmets for babies with oddly shaped heads. This seems to be a side-effect of babies sleeping on their back and modifying the shape of their heads. I've also heard that babies have been rolling and crawling later, in many cases skipping crawling and going straight to walking. They now recommend supervised "tummy time" to help build muscles and skills for crawling that used to just happen when babies were left on their stomach.
All that said, those are really minor side-effects to losing your child.
While I personally don't have anything measurable to back it up, I'd be surprised if it wasn't out there already. Tummy Time's
main goal is to address side effects from "Back to Sleep"[1]. The rest of the things I said came from pediatricians, physical therapists, and other specialists I've talked to about it. Half of the reason I threw out those statements was to see if anyone had more concrete or additional information about those things.
[1] "While it's recommended that you place your baby on his or her back to sleep to reduce the risk of sudden infant death syndrome (SIDS), tummy time gives a baby the chance to experience a different position. This can help reduce the risk of flat spots. Research also suggests that babies who spend time on their tummies crawl on their stomachs earlier than do babies who don't practice tummy time." http://www.mayoclinic.org/healthy-lifestyle/infant-and-toddl...
All that said, those are really minor side-effects to losing your child.