Sleeping on stomach?

Ma

We always put our daughter to bed on her back, but 50% of the time when I go to check on her in the morning she’s sleeping on her stomach. I’ve noticed that on the days when she sleeps on her stomach she sleeps 12+ hours through the night, but when she sleeps on her back she wakes up more easily in the morning as soon as my husband or I start walking around, so she’ll only get 10 hours of sleep. I’m just curious if it’s still recommended for us to put our babies to sleep on their backs, or if it’s okay to put them down on their stomach now? I am worried about SIDS.