Hey Bertie, I love sleeping on my tummy but i couldnt do it after 12-13wks, but my girlfriend did it the whole way through! So go figure, but if you feel comfy sleeping on your tummy when you get a bit bigger then do it, trust me baby will let know if its uncomfy for them they will kick like mad till you move or they will shove a foot under a rib....ohwey. Anyhow good luck sweetie.xx O