The first time I found my daughter sleeping on her tummy, I absolutely panicked. 
I ran upstairs as fast as I could because I was convinced she couldn’t possibly be breathing. When I looked into the crib, her face was completely smushed into the mattress. I gently checked her… and to my surprise, she was breathing just fine.
If your baby is placed on their back to sleep, is using a firm, flat sleep surface, and has reached the milestone of rolling onto their tummy on their own, it’s generally best to leave them there. As hard as it is to watch, they need the opportunity to practice and master this new skill.
If we flip them back over every time they roll, two things can happen. First, we unintentionally create a sleep association where they begin expecting us to come rescue them whenever they roll. Second, we take away valuable opportunities for them to learn how to get comfortable and eventually roll back on their own.
This phase can be nerve wracking for parents, but it usually doesn’t last long. Most babies quickly figure out how to sleep comfortably on their tummy, and many even become tummy sleepers for years to come.
Always place your baby on their back at the start of every sleep, follow safe sleep guidelines, and let them do the rest.