Yes. It is a somewhat dangerous for a baby to sleep on his/her tummy, even though few babies die of sids. Years ago in america, when babies slept on their tummies, about 3 babies out of every 1000 would die of sids. Nowadays, when babies sleep on their backs, about 1 to 1.5 babies per 1000 die of sids. So, the chances dying from sids is higher if sleeping on his/her tummy.
Yes. The preferred position for your baby to sleep is on his or her back. Side positioning is an alternative. Though the stomach sleeping position is comfortable to many infants, this position has been associated with a significant increase in the risk of sids (sudden infant death syndrome). Another risk factor for sids is smoke exposure in the home, so it's best to avoid that as well.