you have to be very wary of even large scale “properly conducted” medical studies. these very same studies are constantly being overturned. the very same pediatricians would have been aghast and highly critical of your parenting skills had you let a baby sleep on their back a few years ago.
if one wants to be a physician and not a medical computer one must use seichel. one must have seichel
this particular study, included low economic classes who tend to fill their babies cribs with soft pillows and fluffy blankets on super soft matresses as they consider this very baby like.
all my grandchilren put their babies to bed on their stomachs. they are more comfortable, sleep better and are less prone to choking. they sleep on firm matresses with none or 1 thin blanket
i am not recommending this as a course of action for anyone here. this is not the CURRENTLY accepted medical advice. please ask your pediatrician