Disparities in Birth Outcomes by Neighborhood Income

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Abstract
Background: Knowledge of socioeconomic disparities in health is of interest to both the general public and public health policymakers. It is unclear how disparities in birth outcomes by socioeconomic status have changed over time, particularly in settings with universal health insurance and favorable socioeconomic conditions. Methods: We identified a cohort of all births (n = 713,950) registered in British Columbia, 1985–2000. We compared rates and relative risks (RRs) of preterm birth, small-for-gestational-age (SGA), stillbirth, and neonatal and postneonatal death across neighborhood-income quintiles from Q1 (richest, the reference) to Q5 (poorest) by 4-year intervals in rural and urban areas. Logistic regression was used to control for maternal and pregnancy characteristics. Results: Maternal characteristics varied widely across neighborhood-income quintiles in both rural and urban areas. There were moderate and persistent disparities in birth outcomes across neighborhood-income quintiles in urban but not rural areas. The relative disparities in urban areas did not diminish over time for all birth outcomes and actually rose for postneonatal mortality. For example, crude RRs (95% confidence intervals) for Q5 versus Q1 in urban areas for SGA were 1.44 (1.37–1.52) in 1985–1988 and 1.41 (1.33–1.49) in 1997–2000; for postneonatal death, the corresponding results were 1.61 (1.17–2.20) and 2.20 (1.24–3.92), respectively. Most of the observed disparities could not be explained by observed maternal and pregnancy characteristics. Conclusion: Moderate disparities in birth outcomes by neighborhood income persist in urban areas (although not rural areas) of British Columbia, despite a universal health insurance system and generally favorable socioeconomic conditions.