Characteristics of infant deaths with positive hair toxicology.

Sudden Unexpected Death in Infancy (SUDI) is the term given to all unexpected infant deaths, comprising accidental, non-accidental and natural deaths including Sudden Infant Death Syndrome (SIDS). As in other developed countries, Australian SUDI rates are relatively low, but incidence rates have remained essentially unchanged since 2004. To increase our understanding of these deaths, we reviewed a cohort of SUDI cases with positive hair toxicology, focussing on toxicology results, pathology findings, and SIDS risk factors. All infant deaths between 1st January 2014 and 31st of December 2023 with positive hair toxicology in the state of Victoria, Australia, were reviewed for toxicology results, pathology findings and SIDS risk factors. A total of 99 infant deaths met the selection criteria. At least one SIDS risk factor was reported in every case, with a median of 5 per case, highlighting that these infants likely had a high cumulative risk for SIDS. Co-sleeping was most common, reported in over 75% of cases. Polysubstance use was high (87%), with a median of 4 drugs detected per case. Methylamphetamine was detected in hair in over half of cases (n = 57, 58%). Postmortem findings including serious illnesses, like pneumonia (p = 0.002), significant neuropathology (p = 0.002 and p = 0.035), low head circumference (< 15th percentile) (p = 0.035) and low body weight (< 15th percentile) (p = 0.022 and p = 0.011) were all positively correlated with drug exposure in hair. Infants with positive hair toxicology appear to have a high cumulative risk for SIDS, which may reflect a chaotic home environment. Most postmortem findings were positively correlated with drug exposure.