County Poverty, Urban-Rural Classification, and the Causes of Term Infant Death United States, 2012-2015

Objective Higher mortality among full-term infants (term infant deaths) contributes to disparities in infant mortality between the United States and other developed countries. We examined differences in the causes of term infant deaths across county poverty levels and urban-rural classification to understand underlying mechanisms through which these factors may act. Methods We linked period birth/infant death files for 2012-2015 with US Census poverty estimates and county urban-rural classifications. We grouped the causes of term infant deaths as sudden unexpected death in infancy (SUDI), congenital malformations, perinatal conditions, and all other causes. We computed the distribution and relative risk of overall and cause-specific term infant mortality rates (term IMRs) per 1000 live births and 95% CIs for county-level factors. Results The increase in term IMR across county poverty and urban-rural classification was mostly driven by an increase in the rate of SUDI. The relative risk of term infant deaths as a result of SUDI was 1.6 (95% CI, 1.5-1.8) times higher in medium-poverty counties and 2.3 (95% CI, 1.2-2.5) times higher in high-poverty counties than in low-poverty counties. Cause-specific IMRs of congenital malformations, perinatal conditions, and death from other causes did not differ by county poverty level. We found similar trends across county urban-rural classification. Sudden infant death syndrome was the main cause of SUDI across both county poverty levels and urban-rural classifications, followed by unknown causes and accidental suffocation and strangulation in bed. Conclusions Interventions aimed at reducing SUDI, particularly in high-poverty and rural areas, could have a major effect on reducing term IMR disparities between the United States and other developed countries.