Why is it recommended that babies sleep on their back?

Babies should be placed on their backs every time they sleep until 1 year of age, because: 

• Babies sleeping on their stomachs have a much greater risk of sleep-related death.
• Stomach sleeping increases the risk of rebreathing the same air that is under the baby’s face. When this happens, a baby who does not rouse and move his or her head can end up with too much exhaled carbon dioxide and not enough oxygen in their blood, a condition that can be fatal.
• Sleeping on the stomach increases a baby’s risk of becoming overheated, as not as much heat is given off in the stomach-sleeping position. Overheating has been associated with greater risk for unexpected infant death.
• In babies 2 to 3 months old, stomach sleeping changes how the nervous system controls the cardiovascular system (how the heart functions) during sleep and can result in a decrease in oxygen to the brain.