- Sudden and unexpected death of an apparently healthy infant, typically occurring between 3 weeks and 5 months of age, most infants dying at night, and not explained by postmortem data.
- Sudden infant death syndrome (sids) is the sudden, unexplained death of an infant younger than one year old. Some people call sids "crib death" because many babies who die of sids are found in their cribs. Sids is the leading cause of death in children between one month and one year old. Most sids deaths occur when babies are between two months and four months old. Although health care professionals don't know what causes sids, they do know ways to reduce the risk. These include
- placing babies on their backs to sleep, even for short naps - "tummy time" is for when babies are awake and someone is watching
- using a firm sleep surface, such as a crib mattress covered with a fitted sheet
- keeping soft objects and loose bedding away from sleep area
- making sure babies don't get too hot - keep the room at a comfortable temperature for an adult
nih: national institute of child health and human development - The abrupt and unexplained death of an apparently healthy infant under one year of age, remaining unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history. (pediatr pathol 1991 sep-oct;11(5):677-84)
- The sudden and unexpected death of a healthy child who is younger than one year old, usually during sleep. The cause of sids is not known.
- Unexpected death in infancy which remains unexplained following autopsy, review of the medical history, and investigation of the death circumstances and death scene.
- Unexpected death of an apparently healthy infant during sleep.
798 Sudden death cause unknown 
798.0 Sudden infant death syndrome convert 798.0 to ICD-10-CM