Baby sleeping face down in mattress

Katie

I’m freaking out! Tonight is the first night we are transitioning our 5.5mo old out of the Merlin sleepsuit and into a sleep sack. She fell asleep and immediately rolled onto her belly and is now sleeping with her face down into the mattress. This is the first time she’s ever not slept on her back. She does not typically have a problem with rolling but I’m terrified that she can’t breathe. Has anyone else had this problem with their baby??