DD was always doing cartwheels in her sleep in the cot, couldnt keep a blanket on her either. Once we moved her into a bed at 14months she had a pillow and blankets and she never had any problems. She no longer moved so much in her sleep but also didnt keep her blankets on either. Like someone else said i was more worried about her not being warm enough but that was easily fixed with sleep suits.

I wouldnt worry to much at there age they will most likely move the blankets out of there way.