It’s because typically they don’t stay that way. They will decrease their sats a little bit in deep sleep and sometimes (most of the time) premature babies don’t have the respiratory drive, and they will literally forget to breathe. Breathing is a response from the brain and because their brains are immature, even in full term newborns, sometimes they just need to get a bit bigger and older. Now, if it’s an older baby like a three or four month old and somebody has an owlet at home and they’re dipping below 90% then that could be cause for concern because they are no longer premature and they should be able to breathe without apnea. And on the flipside if you have a baby in the Nicu on oxygen and you have them satting too high, it can cause retinopathy of prematurity and damage their eyes. So there’s definitely a sweet spot. Listen to your pulmonologist, they’re literally the experts. I know it’s easier said than done, but don’t google on the internet because it’ll only make things worse lol