Unexplained Infant Deaths Without Unsafe Sleep Factors: 2011 to 2020.

OBJECTIVES

To describe sudden unexpected infant deaths (SUIDs) occurring in safe sleep environments and explore differences in selected characteristics.

METHODS

We examined SUID from 22 jurisdictions from 2011 to 2020 and classified them as unexplained, no unsafe sleep factors (U-NUSF). Data were derived from the Sudden Unexpected Infant Death and Sudden Death in the Young Case Registry, a population-based Centers for Disease Control and Prevention surveillance system built on the National Center for Fatality Review and Prevention's child death review program. SUID classified as U-NUSF included infants who were (1) awake, under supervision, and witnessed to become unresponsive or (2) found unresponsive in a safe sleep environment after sleep (unwitnessed). We calculated frequencies and percentages for demographics, birth and environmental characteristics, medical history, and death investigation findings.

RESULTS

Most of the 117 U-NUSF SUID occurred before 4 months of age. Witnessed deaths most commonly occurred at <1 month of age (28%), whereas unwitnessed deaths most commonly occurred at ages 2 to 3 months (44%) Among all U-NUSF, 69% occurred in the infant's home (62% witnessed, 77% unwitnessed). All unwitnessed deaths occurred in a crib; most witnessed deaths occurred while being held (54%) or in a car seat traveling (18%). Most infants (84%) had no history of abuse or neglect. Abnormal autopsy findings were reported in 46% of deaths (49% witnessed, 42% unwitnessed).

CONCLUSIONS

Characterizing these deaths is key to advancing our knowledge of SUID etiology. Our study revealed a heterogeneous group of infants, suggesting physiologic, genetic, or environmental etiologies.