To investigate among US infants born at <37 weeks gestation (a) racial and ethnic disparities in sudden unexpected infant death (SUID) and (b) state variation in SUID rates and non-Hispanic Black (NHB)-non-Hispanic White (NHW) SUID disparity ratio.

In this retrospective cohort analysis of linked birth and death certificates from 50 states from 2005 to 2014, SUID was defined by the following International Classification of Diseases, 9th or 10th edition, codes listed on death certificates: (7980, R95 or Recode 135; ASSB: E913, W75 or Recode 146; Unknown: 7999 R99 or Recode 134). Multivariable models were used to assess the independent association between maternal race and ethnicity and SUID, adjusting for several maternal and infant characteristics. The NHB-NHW SUID disparity ratios were calculated for each state.

Among 4 086 504 preterm infants born during the study period, 8096 infants (0.2% or 2.0 per 1000 live births) experienced SUID. State variation in SUID ranged from the lowest rate of 0.82 per 1000 live births in Vermont to the highest rate of 3.87 per 1000 live births in Mississippi. Unadjusted SUID rates across racial and ethnic groups varied from 0.69 (Asian/Pacific Islander) to 3.51 (NHB) per 1000 live births. In the adjusted analysis, compared with NHW infants, NHB and Alaska Native/American Indian preterm infants had greater odds of SUID (aOR, 1.5;[95% CI, 1.42-1.59] and aOR, 1.44 [95% CI, 1.21-1.72]) with varying magnitude of SUID rates and NHB-NHW disparities across states.

Significant racial and ethnic disparities in SUID among preterm infants exist with variation across US states. Additional research to identify the drivers of these disparities within and across states is needed.