They say back is best for a baby to sleep I have experienced different. My daughter was sleep on her back she spit up started choking and shaking no never again. I let her sleep on her stomach she spits up and moves her head side to side yes it be on her cheeks but she's not choking on it either. So I'll stick with my own theory stomach is best. My son is 4 and slept on his stomach since day 1 home and he's just fine!