Review and special article
Socioeconomic Disparities in Adverse Birth Outcomes: A Systematic Review

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Context

Adverse birth outcomes, such as preterm birth and low birth weight, have serious health consequences across the life course. Socioeconomic disparities in birth outcomes have not been the subject of a recent systematic review. The aim of this study was to systematically review the literature on the association of socioeconomic disadvantage with adverse birth outcomes, with specific attention to the strength and consistency of effects across socioeconomic measures, birth outcomes, and populations.

Evidence acquisition

Relevant articles published from 1999 to 2007 were obtained through electronic database searches and manual searches of reference lists. English-language studies from industrialized countries were included if (1) study objectives included examination of a socioeconomic disparity in a birth outcome and (2) results were presented on the association between a socioeconomic predictor and a birth outcome related to birth weight, gestational age, or intrauterine growth. Two reviewers extracted data and independently rated study quality; data were analyzed in 2008–2009.

Evidence synthesis

Ninety-three of 106 studies reported a significant association, overall or within a population subgroup, between a socioeconomic measure and a birth outcome. Socioeconomic disadvantage was consistently associated with increased risk across socioeconomic measures, birth outcomes, and countries; many studies observed racial/ethnic differences in the effect of socioeconomic measures.

Conclusions

Socioeconomic differences in birth outcomes remain pervasive, with substantial variation by racial or ethnic subgroup, and are associated with disadvantage measured at multiple levels (individual/family, neighborhood) and time points (childhood, adulthood), and with adverse health behaviors that are themselves socially patterned. Future reviews should focus on identifying interventions to successfully reduce socioeconomic disparities in birth outcomes.

Introduction

Adverse birth or pregnancy outcomes—defined here as preterm birth, low birth weight, and small for gestational age—have serious health consequences not only during infancy1, 2 but also throughout childhood3, 4 and in adulthood.5, 6, 7, 8 Socioeconomic and racial/ethnic disparities in preterm birth and low birth weight have been relatively intractable over the past decade.9 Although routine public health statistics in the U.S. historically have been reported by race or ethnic group,10 socioeconomic information on disparities in birth outcomes generally has been limited to maternal educational level. The most recent systematic review of this topic was published in 1987,11 whereas a critical review published in 2000 focused on etiologic factors mediating socioeconomic disparities in pregnancy outcomes.12 Building on those earlier studies, this systematic review focused on the English-language literature from industrialized nations since 2000 that examined links between socioeconomic factors and birth outcomes, with specific attention to the strength and consistency of effects across socioeconomic measures, birth outcomes, and populations.

Section snippets

Evidence Acquisition

Methods for the review were based on those outlined in the Cochrane Collaboration's Handbook for Systematic Reviews of Health Promotion and Public Health Interventions13 and in the Meta-Analysis of Observational Studies in Epidemiology guidelines14 for the reporting of systematic reviews and meta-analyses of observational studies. The systematic review team included five core members: two master's-level researchers with advanced training in epidemiology and biostatistics and three

Evidence Synthesis

Ninety-three of the 106 studies reported a significant association between a socioeconomic measure and an adverse birth outcome, either in the overall study population or in a population subgroup. All 93 of these studies found that adverse birth outcomes were most prevalent among women in the most socioeconomically disadvantaged groups, although two studies also found evidence that higher levels of neighborhood poverty or unemployment were associated with lower prevalence of low birth weight

Discussion

Ninety-three of the 106 studies included in the present review reported a significant association between at least one socioeconomic measure and one birth outcome, either in the overall study population or in a racial/ethnic subgroup. Wherever a significant association was observed, socioeconomic disadvantage was associated with increased risk of adverse birth outcomes across socioeconomic measures, birth outcomes, and countries represented in the current review, except for the two studies that

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