Contributors to excess infant mortality in the U.S. South

Background Infant mortality rates (IMRs) are disproportionally high in the U.S. South; however, the proximate contributors that could inform regional action remain unclear. Purpose To quantify the components of excess infant mortality in the U.S. South by maternal race/ethnicity, underlying cause of death, and gestational age. Methods U.S. Period Linked Birth/Infant Death Data Files 2007-2009 (analyzed in 2013) were used to compare IMRs between the South (U.S. Public Health Regions IV and VI) and all other regions combined. Results Compared to other regions, there were 1.18 excess infant deaths per 1000 live births in the South, representing about 1600 excess infant deaths annually. New Mexico and Texas did not have elevated IMRs relative to other regions; excess death rates among other states ranged from 0.62 per 1000 in Kentucky to 3.82 per 1000 in Mississippi. Racial/ethnic compositional differences, generally the greater proportion of non-Hispanic black births in the South, explained 59% of the overall regional difference; the remainder was mostly explained by higher IMRs among non-Hispanic whites. The leading causes of excess Southern infant mortality were sudden unexpected infant death (SUID; 36%, range=12% in Florida to 90% in Kentucky) and preterm-related death (22%, range= -71% in Kentucky to 51% in North Carolina). Higher rates of preterm birth, predominantly <34 weeks, accounted for most of the preterm contribution. Conclusions To reduce excess Southern infant mortality, comprehensive strategies addressing SUID and preterm birth prevention for both non-Hispanic black and white births are needed, with state-level findings used to tailor state-specific efforts.