Personally I believe it's just plain old common sense. Our grandparents, parents, us and our children would all be dead if what they're saying to young mothers is true today. Sure there is always the exception but honestly, I believe they make these new mothers nervous wrecks worrying over every single thing rather than spend the time loving and using their common sense. If you look up SIDS, they still have no idea what causes it...only theories. Everyone has an expert theory and they change like the wind in all topics. Just look at the new mothers today who have their first child, and then when her second child comes, she no longer has the fears and anxieties placed on her by the so called experts and uses her common sense. I think whatever the mother is comfortable with i.e., a sleeping bag or a blanket is what is appropriate for that mother. As also mentioned quilts on the floor are wonderful for playtime.