Review articleAssociation of neighborhood context with offspring risk of preterm birth and low birthweight: A systematic review and meta-analysis of population-based studies
Introduction
Preterm birth (PTB) and low birthweight (LBW) place an infant at increased risk of morbidity and mortality from neurological, pulmonary and ophthalmic disorders (WHO, 2002). They also increase risk for poor health over the life course, including risk for chronic diseases such as cardiovascular disease (Martin et al., 2013) and type II diabetes mellitus (Martin et al., 2013), costing the nation billions of dollars in health care expenditures and lost earnings potential due to premature death or morbidity. Several risk factors including maternal biological characteristics (e.g. age at delivery) and behaviors (e.g. tobacco and alcohol consumption) have been identified for LBW (David and Collins, 1997, Mumbare et al., 2012) and PTB (Stewart and Graham, 2010, Tepper et al., 2012). Further, disparities in risk for PTB or LBW among racial/ethnic and socioeconomic groups have been well documented. Researchers have looked beyond individual characteristics for factors that may explain risk for LBW and PTB as well as observed disparities (Alio et al., 2010, Wells, 2010). Previous findings from studies examining residential environment, the neighborhood in which mothers lived before or during pregnancy, in relation to LBW and PTB have been inconsistent. Most, although not all (Cubbin et al., 2008), researchers have reported that neighborhood disadvantage increases the risk for poor birth outcomes even after adjusting for maternal covariates (Auger et al., 2009, Collins et al., 2009a, Janevic et al., 2010, Luo et al., 2006, Schempf et al., 2009).
Living in a more disadvantaged economic and social environment can lead to relative deprivation, increased exposure to crime, decreased access to nutritious foods, increased risk of intimate partner abuse, strain from economic instability, and stunted economic growth and social mobility opportunities, all of which can contribute to maternal stress. Maternal stress can lead to higher levels of corticotropin-releasing hormone and cortisol which could trigger contractions and/or the premature rupture of the membrane resulting in PTB (Hodgson and Lockwood, 2010). Maternal stress also leads to the release of catecholamines, such as dopamine, norepinephrine, and epinephrine, into the blood which can cause placental hypoperfusion, a consequence of which is constraint of nutrients and oxygen to the fetus (Rondo et al., 2003) resulting in intrauterine growth retardation and LBW (Wu et al., 2004).
Besides the inconsistency of previous studies, to our knowledge, there are only two published meta-analyses on the association of neighborhood deprivation with PTB (Vos et al., 2014) and LBW (Metcalfe et al., 2011), and neither examined how these associations differ among racial subgroups. In the United States (U.S.), despite decline in racial residential segregation over the last few decades, blacks are still disproportionately represented in areas of higher social and economic disadvantage (Collins et al., 1997, Ellen, 2008, Iceland et al., 2002, O'Campo et al., 1997a, O'Campo et al., 1997b, Pickett et al., 2002). With different social histories, we assumed it possible that the association between neighborhood disadvantage and birth outcomes could differ between these groups. We conducted a systematic review and meta-analysis of the association of neighborhood disadvantage with PTB and LBW to synthesize the results of individual studies in the published literature, analyze differences in the results of these studies, and examine potential differences among racial groups (Walker et al., 2008).
Section snippets
Overview
This systematic review and meta-analysis was based on observational studies conducted in the U.S. using objective measures of primary or secondary data, among native- and foreign-born women, who delivered a live-born infant in the U.S. Data from studies that were conducted among non-Hispanic (NH) white and NH black mothers were used in the current study.
Search strategy and study selection
This study was performed using guidelines established by the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) (Stroup et al., 2000
Results
Information on the characteristics of each study described in the articles (e.g. location, sample size, population, inclusion/exclusion criteria) was abstracted (Supplementary File 2). For the majority (53%) of articles, the census tract was the geographical unit of analysis at the neighborhood level. Overall, those living in the most disadvantaged neighborhoods had a 27% higher risk for PTB compared with those living in the least disadvantaged neighborhoods (OR: 1.27 [95% CI: 1.16, 1.39]);
Discussion
Overall, we found that mothers living in the most disadvantaged, relative to the least disadvantaged, neighborhoods had a 27% higher risk for PTB and 11% higher risk for LBW. Both NH whites and NH blacks were at higher risk for these poor birth outcomes if they lived in the most disadvantaged neighborhoods, albeit the odds ratios were of smaller magnitude among NH blacks. NH white mothers in the most disadvantaged neighborhoods were 48% and 61% more likely to have PTB and LBW infants,
Conclusion
In this systematic review and meta-analysis, we found that overall, neighborhood disadvantage is associated with PTB and LBW in race-stratified, but not race-adjusted, models. Furthermore, we found that associations among NH whites were much stronger than associations among NH blacks.
Acknowledgments
We would like to thank Barbara Folb, Public Health Informationist at the University Of Pittsburgh Graduate School Of Public Health, for assisting with the search strategy design, and Brian McGill, doctoral student in the University Of Pittsburgh Department Of Statistics, for reviewing the meta-analysis methodology. Dr. Ncube was supported by the Reproductive, Perinatal and Pediatric Epidemiology Training Program of the National Institute of Child Health and Human Development (T32 HD052462).
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