If your crib mattress has air valves on the side (like from potterybarn) the air has nowhere to go tucked into the side of the upholstery bed, or underneath. In our crib there was the metal rack beneath with plenty of airflow.  Th bed is cute and soft, but cradled into it, our mattress constantly fills up with air in the middle after laying on it. The mattress needs to breathe! And cannot in this bed.  I can’t speak to other mattresses.  

Why does this matter The built up air changes the shape of the mattress and puffs it up in the middle so the toddler rolls off to the side.  It’s changes the comfort and structure of the mattress. 

Hard to give a review for this reason, if the mattress were different for us it may be a completely different experience so keep that in mind!  Otherwise it’s a soft and darling toddler bed.