Explaining Sudden Unexpected Infant Deaths, 2011-2017

Abstract

Background: Sudden unexpected infant death (SUID) represents a broad group of explained and unexplained infant deaths (<1 year old). Explaining why SUID occurs is critical to understanding etiology and prevention. Death certificate data cannot differentiate explained from unexplained SUID cases nor describe the surrounding circumstances. We report SUID rates by explained and unexplained categories and describe demographics and history of recent injury or illness using the Centers for Disease Control and Prevention SUID Case Registry.

Methods: The registry is a population-based surveillance system built on Child Death Review programs. Data are derived from multiple sources, including death certificates, scene investigations, and autopsy reports. Cases included SUIDs reported by states or jurisdictions participating in the registry during 2011-2017. Cases were classified into explained and unexplained categories by using the registry's classification system. Frequencies, percentages, and mortality rates per 100 000 live births were calculated.

Results: Of the 4929 SUID cases, 82% were categorized as unexplained. Among all cases, 73% had complete case information. Most SUIDs (72%) occurred in an unsafe sleep environment. The SUID mortality rate was 97.3 per 100 000 live births. Among explained and possible suffocation deaths, ∼75% resulted from airway obstruction attributed to soft bedding.

Conclusions: Unsafe sleep factors were common in explained and unexplained SUID cases, but deaths could only be classified as explained suffocation for ∼20% of cases. Further analysis of unexplained deaths, including continued improvements to death scene investigation and documentation, may generate hypotheses for physiologic and genetic research, advance our understanding of gaps in SUID investigation, and enhance our understanding of infants at highest risk.

Keywords: CDC; CDR; Centers for Disease Control and Prevention; Child Death Review; DSI; NAME Panel; NFR-CRS; National Association of Medical Examiners’ Panel on Sudden Unexpected Death in Pediatrics; National Fatality Review Case Reporting System; SIDS; SUID; death scene investigation; sudden infant death syndrome; sudden unexpected infant death.

FIGURE 1

SUID categorization guide. ^a An autopsy must include an internal examination. ^b Death investigation = any agency obtaining information about the circumstances of the death; this does not need to include a visit to the scene or need to have complete information. ^c When there is conflict, use the expertise of your multidisciplinary team and all of the evidence to figure out what really happened. If there is enough evidence for the team to resolve the conflict, then document the team’s decision in the narrative and continue down the algorithm. If the evidence does not reveal a clear resolution, then document the sustaining conflict and treat it as an unknown. Refrain from making assumptions and err on the side of an unknown. ^d Consideration of lividity may be useful in verifying position, but lack of information on lividity does not make the case incomplete. Lividity that indicates supine positioning could be from flipping the infant after death and should be considered cautiously. ^e Answer no if the infant was not sleeping. ^f Infant was put in a car seat (1) to sleep (should continue down the algorithm); (2) to travel, not sleep, with soft objects or loose bedding (should continue down the algorithm); or (3) to travel, not sleep, with no soft objects or loose bedding (should be categorized as “unexplained, no unsafe sleep factors”). ^g Includes infants who were witnessed going unresponsive. ^h Needs to be assigned at least 1 mechanism using the following definitions (the following are examples, not a comprehensive list): (1) soft bedding: when an infant’s airway is obstructed by a blanket, sheet, pillow, couch or recliner cushions, or other soft objects of loose bedding that are part of the immediate sleep environment: (a) nose and/or mouth obstructed at the intersection of soft bedding (eg, where a pillow and mattress meet, where the back and seat of a couch meet); (2) wedging: when an infant’s airway is obstructed as a result of being stuck or trapped between inanimate objects: (a) wedged with face clear (eg, in gap, face above mattress), chest or neck obstruction only; (3) overlay: when a person rolls on top of or against an infant, obstructing the infant’s airway: (a) overlay with face clear (obstructed chest or neck only), (b) face into person with or without chest or neck obstruction, and (c) infant pinned between person and couch, facing person (Surface sharing only is not enough evidence for overlay. An overlay needs to be witnessed, eg, someone waking up on top of an infant or someone seeing someone else on top of an infant.); (4) other: when an infant’s airway is obstructed by something in the sleep environment other than soft bedding, overlay, or wedging, such as a plastic bag (“other” should not be selected for unsafe sleep factors, such as prone positioning or impaired caregivers); and (5) multiple mechanisms: (a) wedging and soft bedding: (i) wedged with face into soft bedding (mattress, pillow, blankets), nose and mouth obstructed, and (ii) wrapped or entangled in blankets and wedged; (b) overlay and soft bedding: (i) overlay with nose and/or mouth obstructed by soft bedding (mattress, pillow, blankets) and (ii) infant pinned between person and couch and facing couch. ⁱ Examples include the following: (1) a 1-month-old infant found face down in a pillow with her nose and mouth fully obstructed, (2) a 2-month-old infant found with her head and face wedged between the cushions at the back of the sofa, and (3) a 4-month-old infant found lifeless in a twin bed with his head and body underneath his mother. ^j Includes infants whose airways were obstructed by a Consumer Product Safety Commission–approved mattress used as recommended in a crib, portable crib, or bassinet.

FIGURE 2

Mechanisms of explained or possible suffocation occurring in an unsafe sleep environment specified in the CDC SUID Case Registry classification system.