Not even head to the side - properly face down.
It horrifies me when I see him in this position, he has done it since we put him in his cot-bed as I think he had room to move when he didn't in the crib in our room.
I gently roll him over when I see he has moved into this position but he is a light sleeper and wakes slightly (very grumpily) and will roll back onto his side with his neck extended back and then straight onto his front again. Face down.
He has a dummy and is in a sleeping bag and can move around the cot with ease on his tummy but his ability to roll back is sporadic (although easier in a sleeping bag somehow)
So, what are the risks of this do you think? Should I stop worrying or keep encouraging him to sleep on his back? FWIW he has reflux (medicated) so may be more comfortable on his front. He is on a pocket sprung mattress with a coolmax lining if that makes any difference (better than foam perhaps?)