Comment by LeonardoTolstoy

It says that there is like a 10x risk of SIDS in the first four months of life with tummy sleeping.

I don't agree with her on everything, but Emily Oster's chapter on SIDS (in the second book I think, Cribsheet) I think does a good job outlining the data on it. And my brother just had a kid who also would absolutely not sleep on his back. Once he could roll he just sleeps on his tummy (but once they can roll SIDS is not really an issue)