Sudden infant death syndrome (SIDS) has no symptoms or warning signs. Babies who die of SIDS:

• Cannot be revived (resuscitated).
• Seem healthy before being put to bed.
• Show no signs of having struggled. The baby is often found in the same position as when he or she was put to bed.

Only about 5% of babies who die of SIDS have a history of apparent life-threatening events (ALTE), and the relationship between SIDS and ALTE is unclear.¹ During ALTE, a baby has abnormally long pauses in breathing (longer than 20 seconds). The skin changes color (bluish and blotchy) or becomes pale, and the body stiffens and then goes limp. The baby may also choke or gag. One or more ALTE events have been suspected in some babies who later died of SIDS. However, machines (apnea monitors) that are commonly used to detect these periods of interrupted breathing have not been effective in preventing SIDS.