Past generations may have recommended newborns sleep on their tummies, but we know more today. Back is best, and this is strongly supported by research. Once your baby is older (4-5 months+) and can independently roll, it’s okay to let them stay in positions they get into themselves, but you’ll still place them down on their back initially. If your newborn rolls in their sleep, it is likely unintentional, and for the utmost safety, they will need your help being repositioned onto their back.