As with soft bedding, prone sleeping puts more of the baby's body in contact with the bed. Sleeping this way also puts the baby's face in contact with the bed, further reducing heat loss through the head. Bed Sharing Heat from other people in the same bed may contribute to higher body temperatures. Guntheroth and Spiers also point out that babies who sleep with their mothers often have their heads covered by blankets. Most heat is lost from blood vessels through the skin.
Nicotine constricts peripheral blood vessels and therefore can reduce heat loss.
Each of these factors may raise an infant's body temperature to levels that interfere with the brain's ability to control temperature and breathing. Babies should NOT sleep on soft bedding. Babies should NOT have their heads covered when they sleep. These are fairly simple ways to reduce the risks of SIDS and to avert a tragedy.