Baby mattress

Is it true that its bad for newborn to sleep on soft mattress? If yes at what age they can sleep on soft mattress? Thanks
1 Reply
sleeping on soft mattress increased the risk of's really not necessary to put baby or children to sleep on soft mattress.
I read that it is bad in case the baby put to sleep on their stomach. But how about the one sleep on their back is there any bad effect (their backbone development for example)