Low birth weight: a women's health issue

Association of neighborhood context with offspring risk of preterm birth and low birthweight: A systematic review and meta-analysis of population-based studies

Findings from studies investigating associations of residential environment with poor birth outcomes have been inconsistent. In a systematic review and meta-analysis, we examined associations of neighborhood disadvantage with preterm birth (PTB) and low birthweight (LBW), and explored differences in relationships among racial groups. Two reviewers searched English language articles in electronic databases of published literature. We used random effects logistic regression to calculate odds ratios (and 95% confidence intervals) relating neighborhood disadvantage with PTB and LBW. Neighborhood disadvantage, most disadvantaged versus least disadvantaged neighborhoods, was defined by researchers of included studies, and comprised of poverty, deprivation, racial residential segregation or racial composition, and crime. We identified 1314 citations in the systematic review. The meta-analyses included 7 PTB and 14 LBW cross-sectional studies conducted in the United States (U.S.). Overall, we found 27% [95%CI: 1.16, 1.39] and 11% [95%CI: 1.07, 1.14] higher risk for PTB and LBW among the most disadvantaged compared with least disadvantaged neighborhoods. No statistically significant association was found in meta-analyses of studies that adjusted for race. In race-stratified meta-analyses models, we found 48% [95%CI: 1.25, 1.75] and 61% [95%CI: 1.30, 2.00] higher odds of PTB and LBW among non-Hispanic white mothers living in most disadvantaged neighborhoods compared with those living in least disadvantaged neighborhoods. Similar, but less strong, associations were observed for PTB (15% [95%CI: 1.09, 1.21]) and LBW (17% [95%CI: 1.10, 1.25]) among non-Hispanic black mothers. Neighborhood disadvantage is associated with PTB and LBW, however, associations may differ by race. Future studies evaluating causal mechanisms underlying the associations, and racial/ethnic differences in associations, are warranted.

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.

Neighborhood effects on birthweight: an exploration of psychosocial and behavioral pathways in Baltimore, 1995--1996

Neighborhood characteristics have been proposed to influence birth outcomes through psychosocial and behavioral pathways, yet empirical evidence is lacking. Using data from an urban, low-income sample, this study examined the impact of the neighborhood environment on birthweight and evaluated mediation by psychosocial and behavioral factors. The sample included 726 women who delivered a live birth at Johns Hopkins Hospital in Baltimore, Maryland, USA between 1995 and 1996. Census-tract data were used to create a principal component index of neighborhood risk based on racial and economic stratification (% Black, % poverty), social disorder (violent crime rate), and physical deterioration (% boarded-up housing) (alpha=0.82). Information on sociodemographic, psychosocial, and behavioral factors was gathered from a postpartum interview and medical records. Random intercept multilevel models were used to estimate neighborhood effects and assess potential mediation. Controlling for sociodemographic characteristics, a standard deviation increase in neighborhood risk conferred a 76g birthweight decrement. This represents an approximate 300g difference between the best and worst neighborhoods. Although stress (daily hassles), perceived locus-of-control, and social support were related to birthweight, their adjustment reduced the neighborhood coefficient by only 12%. In contrast, the neighborhood effect was reduced by an additional 30% and was no longer statistically significant after adjustment for the behavioral factors of smoking, drug use, and delayed prenatal care. These findings suggest that neighborhood factors may influence birthweight by shaping maternal behavioral risks. Thus, neighborhood level interventions should be considered to address multiple maternal and infant health risks. Future studies should examine more direct measures of neighborhood stress, such as perceived neighborhood disorder, and evaluate alternative mechanisms by which neighborhood factors influence behavior (e.g., social norms and access to goods and services).

Birth outcomes among urban African-American women: a multilevel analysis of the role of racial residential segregation

Residential segregation is a common aspect of the urban experiences of African-Americans in the United States (US), yet few studies have considered how segregation might influence perinatal health. Here, we develop a conceptual model of relationships between segregation and birth outcomes and test the implications of the model in a sample of 434,376 singleton births to African-American women living in 225 US Metropolitan Statistical Areas (MSAs). Data from the National Center for Health Statistics 2002 birth files were linked to data from the 2000 US Census and two distinct measures of segregation: an index of isolation (the probability that an African-American resident will encounter another African-American resident in any random neighborhood encounter) and an index of clustering (the extent to which African-Americans live in contiguous neighborhoods). Using multilevel regression models, controlling for individual- and MSA-level socioeconomic status and other covariates, we found higher isolation was associated with lower birthweight, higher rates of prematurity and higher rates of fetal growth restriction. In contrast, higher clustering was associated with more optimal outcomes. We propose that isolation reflects factors associated with segregation that are deleterious to health including poor neighborhood quality, persistent discrimination and the intra-group diffusion of harmful health behaviors. Associations with clustering may reflect factors associated with segregation that are health-promoting such as African-American political power empowerment, social support and cohesion. Declines in isolation could represent positive steps toward improving birth outcomes among African-American infants while aspects of racial contiguity appear to be mitigating or indeed beneficial. Segregation is a complex multidimensional construct with both deleterious and protective influences on birth outcomes, depending on the dimensions under consideration. Further research to understand racial/ethnic and economic health disparities could benefit from a focus on the contributory role of neighborhood attributes associated with the dimensions segregation and other social geographies.