BACKGROUND AND PURPOSE:

• Most studies investigating sudden unexpected infant death (SUID) combine all cases, regardless of age or cause and will include SIDS  
• Lavista Ferres et al. (Pediatrics, 2019) examined whether there are statistically different subcategories of SUID based on the age of occurrence

METHODS:

• Retrospective, cross-sectional analysis (2003 to 2013)
• Data
  • CDC Birth Cohort Linked Birth/Infant Death Data Set (2003–2013)
• Data analysis
  • Logistic regression models developed to identify subpopulations of SUID cases based on age
  • Follow up analysis to determine whether there are a set of specific covariates specific to the various age groups

RESULTS:

• 41,125,233 births | 37,624 followed with SUID
  • Largest peak on day 0, which then declined with a 2^nd peak between 1 to 4 months of age
• Two groups were identified
  • Sudden unexpected early neonatal deaths (SUENDs): Occurrence days 0 to 6
    • Could be distinguished based on factors with a 77.3% probability
  • Postperinatal SUIDs: Occurrence days 7 to 364

There were significant differences between the groups for the following

• ICD10 codes
  • R99: Ill-defined and unknown cause of mortality)
    • SUENDs: 67%
    • Postperinatal: 28%
  • R95: SIDS
    • SUENDs: 24%
    • Postperinatal: 55%
  • W75: Accidental suffocation and strangulation in bed
    • SUENDs: 9%
    • Postperinatal: 17%
• Increasing live birth order
  • Higher risk for postperinatal group (i.e., when compared to first born, increasing birth order increased risk)
  • SUENDs: 43% were first live birth
  • Postperinatal: 29% were first live birth
• Marital status
  • Unmarried women had a higher risk for postperinatal SUID
  • Being unmarried was protective for SUEND
• Age of mother
  • Younger mothers (ages 15–24) had higher postperinatal SUID rates but lower SUEND rates
  • Rates of both were lower if mothers were >30 years
• Birth weight
  • SUENDs had 2 peaks in birth weight distribution
    • First peak: Extremely low birth weights (m500 g and/or gestational length <28 weeks)
    • Second peak: 3000 to 3499 g
  • Postperinatal: Also associated with low birth weights but not as large an association as with SUENDs
• Maternal smoking
  • First 48 hours: Not associated with risk for either group
  • >48 hours: Significant association with peak on day 21
    • aOR 2.34 (95% CI, 1.79 to 2.89; P <0.001)

CONCLUSION:

• The authors conclude that
  • SUEND (days 0–6) should be considered a separate entity from postperinatal SUID in future studies
  • “Differences in risk factors between our SUEND and postperinatal SUID populations suggest that underlying mechanisms are separate and do not lie on a continuum”
  • “Back to sleep” guidance reduced postperinatal SIUD but not SUENDs
  • SUEND with low birthweight should perhaps be reclassified and coded as “disorders related to short gestation and low birth weight”
  • Maternal smoking was the “greatest modifiable risk factor for SUID and regardless of amount smoked, doubles the risk after 48 hours

Learn More – Primary Sources:

Distinct Populations of Sudden Unexpected Infant Death Based on Age

CDC: Sudden Unexpected Infant Death and Sudden Infant Death Syndrome

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Pregnancy-Related Deaths in the U.S.: How Many are Preventable?

Is there any Link between Maternal Vaccinations and Infant Hospitalizations or Death? 6 Month Infant Follow-up