Contribution of previable births to infant mortality rate racial disparity in the United States

Objective: To quantify racial differences in contribution of previable live births (<20 weeks gestational age (GA)) to United States (US) Infant Mortality Rates (IMR). Methods: Population-based retrospective cohort of US live births (2007–14) using CDC WONDER database stratified by maternal race/ethnicity. We compared the contribution of previable births to IMR and calculated modified IMRs (≥20 weeks GA) excluding previable live births in each group. Contingency tables and chi-square calculations were performed to detect differences between groups. Results: Previable deaths represented 4.1%, 7.7%, and 5.0% of total deaths for nonHispanic white, nonHispanic black, and Hispanic, respectively. Previable contribution to total IMR are 0.21, 0.89, and 0.26 per 1000 live births (P < 0.0001). Modified IMRs are 4.98, 10.85, and 4.69 deaths per 1000 live births. Conclusion: IMR standardization with a minimum GA may obscure the disproportionate contribution of previable births to IMRs among the black population, which has the largest proportion of previable births.