Depends on how poor the baby sleeps when on back. If he/she wakes up like every 1-2 hrs, you don't have much of a choice. My baby sleeps on her tummy since about 2mo, for that reason. We don't have bumpers in the crib (which aew not suggested anyway), and keep a fan running. Professionals still don't know what really causes SIDS, but stats show fans are correlated with 72% less of deaths. So I guess it's worth a try.