Firstly, OMG I can't believe Adeline is 6 months old already!

Oskar sleeps on his tummy all the time too, rolls over straight away and little bum in the air. He actually quite often moves until he has his head in the corner and sleeps all night like that. I can't even remember how old he was when he started sleeping on his tummy. Once they can roll around there's really not a lot you can do to prevent it. Think of how you or hubby sleep. Oskar sleeps in the same kinda position as me (except I don't have my bum in the air - lol). We move around in our sleep and as they get mobile so do they. We have the airwrap that Sacha is talking about and it is great.