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About SUID and SIDS

Understanding the Problem

 SIDS Blocks
About 4,000 infants (less than one year of age) die suddenly and unexpectedly each year in the United States. Learn more about the problem and CDC activities to monitor and reduce sudden unexpected infant death.

Nearly 4,000 US infants die suddenly and unexpectedly each year. We often refer to these deaths as sudden unexpected infant death (SUID). Although the causes of death in many of these children can’t be explained, most occur while the infant is sleeping in an unsafe sleeping environment.

Researchers can’t be sure how often these deaths happen because of accidental suffocation from soft bedding or overlay (another person rolling on top of or against the infant while sleeping). Often, no one sees these deaths, and there are no tests to tell sudden infant death syndrome (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.

Law enforcement, first responders, death scene investigators, medical examiners, coroners, and forensic pathologists all play a role in carrying out the case investigation.

A thorough case investigation includes

  • An examination of the death scene.
  • An autopsy (medical examination of the body after death).
  • A review of the infant’s medical history.

Most SUIDs are reported as one of three types of infant deaths.

Types of SUID

  • Sudden Infant Death Syndrome (SIDS)
    SIDS is defined as 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. SIDS is the third leading cause of infant deaths in the United States and the leading cause of death in infants 1 to 12 months old.
  • Unknown Cause
    The sudden death of an infant less than 1 year of age that cannot be explained because a thorough investigation was not conducted and cause of death could not be determined.
  • Accidental Suffocation and Strangulation in Bed
    Mechanisms that lead to accidental suffocation include
    • Suffocation by soft bedding—such as a pillow or waterbed mattress.
    • 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—such as when an infant’s head and neck become caught between crib railings.

Even after a thorough investigation, it is hard to tell SIDS apart from other sleep-related infant deaths such as overlay or suffocation in soft bedding. While an observed overlay may be considered an explained infant death, no autopsy tests can tell for certain that suffocation is the cause of death.

What Is CDC Doing About SUID and SIDS?

A better understanding of the circumstances and events associated with sleep-related infant deaths may help reduce future deaths. CDC’s activities aim to standardize and improve data collected at infant death scenes and promote consistent reporting and classification of SUID cases. These activities help local and state teams to improve investigation systems by changing practices, policies, and creating data-driven interventions to reduce risk, such as safe sleep education and promotion.

CDC Resources and Activities

Sudden Death in the Young Registry

Sudden Death in the Young Registry

CDC and the National Institutes of Health are working together to create the Sudden Death in the Young Registry to get better information on sudden unexpected deaths among young people up to age 19 in the United States.

Image of a baby sleeping with text Safe to Sleep

Safe to Sleep

CDC collaborates with the National Institutes of Health in its Safe to Sleep campaign, formerly known as the Back to Sleep campaign. Safe to Sleep has outreach and education activities aimed at reducing infant death from sudden infant death syndrome (SIDS) and other sleep-related infant deaths.

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