740: Contribution of previable infant deaths to infant mortality rates among US census regions

Abstract

Variation in reporting of early gestation births has the potential to influence infant mortality rate (IMR) calculations and affect regional IMR comparisons. We aim to quantify differences in the contribution of early previable live births (<20 weeks) to United States (US) regional IMRs. Population-based cohort study of all US live births and infant deaths, 2007-2014, using CDC Linked Birth/Infant Death records from WONDER database, which reports births from 17-47 wks. We compared the proportion of infant deaths attributable to birth <20 wk vs 20-47 wk across four US census regions (North, South, Midwest, and West). We calculated adjusted IMR representing only births ≥20 wks. Difference between reported and adjusted IMRs (ΔIMR) was compared between US regions with X2. Percentage of infant deaths attributable to birth <20wk was 6.3%, 6.3%, 5.3%, and 4.1% of total deaths for the Northeast, Midwest, South, and West, respectively, p<0.0001. The contribution of these deaths to each region’s IMR was 0.34, 0.42, 0.37, and 0.2 per 1000, respectively. A standardized IMR definition of births ≥20wk yielded less regional variation and lower IMRs of 5.1, 6.2, 6.6, and 4.9 per 1000. Recording <20wk deliveries as live births contributes significantly to IMR as all result in infant death. These may be considered miscarriage by some providers and not be recorded as live births. We demonstrate that standardized IMR reporting defining live birth at ≥20wk results in more consistent IMRs among US regions. We identified a higher IMR difference in regions that currently report the highest IMRs, the Midwest and South. Standardized reporting would result in US IMR rates comparable to the Healthy People 2020 goal of 6.0 per 1000. Since IMR is an important indicator of population health, with significant governmental policy implications, validity of regional and international comparisons could be strengthened through standardization of infant death reporting in the US.