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About SUID and SIDS

Learn more about the problem and types of Sudden Unexpected Infant Death (SUID).

Understanding the Problem

In 2014, there were about 3,500 sudden unexpected infant deaths (SUID) in the United States. SUID is the death of an infant less than 1 year of age that occurs suddenly and unexpectedly, and whose cause of death is not immediately obvious before investigation. Most SUIDs are reported as one of three types.

Types of SUID

  • Sudden Infant Death Syndrome (SIDS)children's alphabet blocks spelling "SIDS"
    The sudden death of an infant less than 1 year of age that cannot be explained after a thorough investigation is conducted, including a complete autopsy, examination of the death scene, and a review of the clinical history. About 1,500 infants died of SIDS in 2014. SIDS is the leading cause of death in infants 1 to 12 months old.
  • Unknown Cause
    The sudden death of an infant less than 1 year old that remains undetermined because one or more parts of the investigation was not completed.
  • Accidental Suffocation and Strangulation in Bed
    The sudden death of an infant less than 1 year of age that can happen because of
    • Suffocation by soft bedding—for example, when a pillow or waterbed covers an infant's nose and mouth.
    • Overlay—when another person rolls on top of or against the infant while sleeping.
    • Wedging or entrapment—when an infant is wedged between two objects such as a mattress and wall, bed frame, or furniture.
    • Strangulation—for example, when an infant’s head and neck become caught between crib railings.


Even after a thorough investigation, it can be hard to tell SIDS apart from other sleep-related infant deaths such as overlay or suffocation by soft bedding. This is because these deaths are often unwitnessed and there are no tests to tell SIDS apart from suffocation. To complicate matters, people who investigate SUIDs may report cause of death in different ways and may not include enough information about the circumstances of the event from the death scene.

What Is CDC Doing About SUID and SIDS?

CDC’s Division of Reproductive Health has SUID monitoring programs in 16 states and 2 jurisdictions, covering 30% of all SUID cases in the United States. Participating states and jurisdictions use data about SUID trends and circumstances to develop strategies to reduce future deaths. Learn more about CDC resources and activities to address SUID and SIDS.


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