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Study: SUID risk factors differ in first week vs. first year :

December 9, 2019

Different risk factors may contribute to sudden unexpected infant death (SUID) in the first week of life vs. the rest of the first year, according to a new study.

Cause of death, birth order, birthweight, and the mother’s age and marital status each differed between the two groups.

Researchers analyzed data from the Centers for Disease Control and Prevention (CDC) Birth Cohort Linked Birth/Infant Death Data Set 2003-2013, which included more than 41 million live births and 37,624 SUID deaths. SUID includes deaths from sudden infant death syndrome (SIDS), unknown causes and accidental suffocation/strangulation in bed, according to “Distinct Populations of Sudden Unexpected Infant Death Based on Age,” (Lavista Ferres JM, et al. Pediatrics. Dec. 9, 2019,

The team compared SUID deaths on each day to deaths occurring on other days during the infant’s first year and found those on days 0-6, called sudden unexpected early neonatal deaths (SUEND), were distinct from those occurring on days 7-364, known as postperinatal SUID. The largest peak in deaths was on the first day of life, and this peak was linked to extremely low birthweights.

About 67% of SUEND were due to unknown causes, 24% were from SIDS and 9% were classified as suffocation/strangulation in bed. Among postperinatal SUID, 55% were classified as SIDS, 28% had an unknown cause and 17% were suffocation/strangulation in bed.

Infants were at increased risk of SUEND if they were of lower live birth order or had a mother who was married. Risk of SUID death increased with higher live birth order, an unmarried mother or young mother.

While low birthweight was linked to deaths in both periods, the rates were greater for SUEND. Smoking during pregnancy also was linked to deaths in both periods, but the risk was more significant for postperinatal SUID.

“On the basis of these differences in risk factors and developmental windows, we propose that SUIDs that occur in the first week of life are a distinct etiology and should consistently be considered separately from postperinatal SUID cases,” authors wrote. “Considering these 2 populations discretely may help uncover independent underlying physiological mechanisms and/or genetic causes underlying SUEND and SUPC (sudden unexpected postnatal collapse) versus postperinatal SUIDs.”

The author of a related commentary called the study an “important contribution to the conversation” around SUID but also noted deaths on the first day are challenging to characterize as half of stillbirths occur during labor.

“Research on SIDS and stillbirths suggests a biological continuum between fetal vulnerabilities and SIDS, not a disconnect,” he wrote. … “Although Lavista Ferres et al’s research may point to an area that requires new thinking, misclassification may exaggerate the differences within SUID and mask these commonalities.”

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