Honestly, i dont think i matters, when my son was born almost 4 years ago, i was told on his side, but he would roll over to his tummy (no kidding he was doing this the day he was born), the nurse at the hospital said if that is the way he is comfy then let him be, just make sure his head is turned to the side and no blankets near his face. When my other son was born almost 2 yrs ago they told me the same thing which ever way he was comfy. My friend just had her baby 2 days ago and the nurses at the hospital were putting him on his side. The positions with sids change every few years (actually i dont think they really know but that is just my opinion.) Im not sure what the rule is on day care providers (my kiddos have never been) but you just have to remember this is YOUR baby not hers (30 yrs experience or not), and remember alot of things they did back then we are told now by pedis not to do, i think its just up to the parent and what makes you comfortable, if you want him to sleep on his back, then just politly tell her i would perfer it if he sleeps on his back, im sure she would understand and not take it harshly, and if she does then you might want to find someone else if she will take that (as such a small request) personally, then when he gets older (if he is still going then) she will probably be the same, and those things might be more important to you then this is. Sorry if i offended you or anyone else this is just my own opinion. Hope this helps ya.