Objective. To determine the effect of racial inequalities in sociodemographic factors, state fetal death registration requirements and reporting of non-viable births and perinatal regionalization, defined as birth hospital level and neonatal intensive care unit (NICU) transfer, on nationwide variation in racial disparities in infant mortality (IM).

Methods. National Center for Health Statistics (NCHS) live birth and linked infant death records from 2000-2002, U.S. Bureau of the Census, 2000 Census of Population and Housing, and Michigan Department of Community Health live birth and linked infant death vital records from 1996-2006 were used to examine absolute (black IM/white IM) and relative (black IM–white IM) racial disparities in IM rates.

Results. Absolute and relative U.S. disparity measures were 6.99 per 1,000 live births and 2.42, respectively. The absolute disparity measure was highly correlated with black IM (r = 0.91) but not white IM (r = -0.03), while the relative measure was correlated with both black IM (r = 0.57) and white IM (r = -0.51). Compared to racial inequalities in other infant, maternal and state risk factors, inequalities in the proportion of very low birthweight births were most correlated with disparities in IM. Mortality rates and racial disparities were the highest among states with birthweight only fetal death reporting criteria and among states with the highest proportion of non-viable births recorded in birth certificates (RR=1.22; 95% CI=1.17-1.37). The largest proportion of this difference was accounted for by births ≤ 22 weeks gestation (RR=1.71; 95% CI=1.43-2.04). The case study in Michigan found that the majority of infants were born at a level 3 hospital. The highest IM rates were seen among extremely preterm infants born at level 1 hospitals compared to their level 3 counterparts (level 1 465.3 per 1,000 live births; level 3 = 363.9 per 1,000 live births) and among extremely preterm level 1 white births compared to their black counterparts (white = 506.1 per 1,000 live births; black 383.3 per 1,000 live births). Extremely preterm black infants who were born at a level 1 hospital and subsequently transferred to the NICU had a significantly decreased risk of infant death, compared to their white counterparts (RR=0.41; 95% CI=0.26-0.66).

Conclusion. Racial inequalities in the proportion of very low birthweight and very preterm infant births along with state differences in reporting very low birthweight and very preterm births were consistently associated with national variation in IM disparities. Racial inequalities in perinatal regionalization did not account for higher infant or neonatal mortality rates among black infants. A uniform definition of fetal death should be adopted to reduce systematic differences in the reporting of live births and fetal deaths, especially among deaths ≤ 22 weeks gestation. Efforts should be made to reduce rates of extremely preterm and extremely low birthweight births where mortality rates and racial disparities in risk of adjusted mortality were the highest and state disparities were more correlated.