The association between neighbourhoods and adverse birth outcomes: a systematic review and meta-analysis of multi-level studies.

Many studies have examined the role of neighbourhood environment on birth outcomes but, because of differences in study design and modelling techniques, have found conflicting results. Seven databases were searched (1900-2010) for multi-level observational studies related to neighbourhood and pregnancy/birth. We identified 1502 articles of which 28 met all inclusion criteria. Meta-analysis was used to examine the association between neighbourhood income and low birthweight. Most studies showed a significant association between neighbourhood factors and birth outcomes. A significant pooled association was found for the relationship between neighbourhood income and low birthweight [odds ratio = 1.11, 95% confidence interval: 1.02, 1.20] whereby women who lived in low income neighbourhoods had significantly higher odds of having a low birthweight infant. This body of literature was found to consistently document significant associations between neighbourhood factors and birth outcomes. The consistency of findings from observational studies in this area indicates a need for causal studies to determine the mechanisms by which neighbourhoods influence birth outcomes.