Abstract
Background
The majority of research to date on low birthweight (LBW) has emphasized maternal characteristics, and less so how maternal risk is shaped (via contextual factors). This study aims to understand how neighbourhood characteristics influence LBW, independently and in interaction with individual factors, in the context of community-defined neighbourhoods.
Method
All singleton births for a 3-year period (1992-1995; n=8504) to mothers resident in Saskatoon comprised the study population. Data included were child and mother’s/father’s characteristics and six neighbourhood characteristics: socio-economic disadvantage, social disconnection, physical condition, population density, availability and accessibility of local programs and services, and smoking prevalence. Multilevel modeling for a binary outcome (LBW) was employed; odds ratios and 95% confidence intervals for the final model were reported.
Results
Newborns in families receiving income assistance, with a mother over 40, and whose mother had previous stillbirths were at greater risk for LBW; however, mothers who had more than one previous live birth were less likely to have a LBW baby. Independent of individual-level risk factors, infants in socio-economically disadvantaged neighbourhoods were at increased risk for LBW (OR 1.34; 95% CI 1.07, 1.68). Most interestingly, the risk of LBW among infants born to single mothers was exacerbated by greater level of neighbourhood social disconnection. Neighbourhoods with low levels of social disconnection have a lower risk of LBW among single mothers (OR=0.89, 95% CI 0.72, 1.17) compared to those with high levels (OR=1.57, 95% CI 1.18, 1.93).
Conclusion
Neighbourhood contextual factors influence the risk of LBW directly, via independent effects, as well as through moderating the risk of individual factors. Studies that simultaneously examine both individual and contextual effects on LBW could provide a stronger evidentiary base for multiple points of interventions targeting individuals as well as settings.
Key words: Infant, low birth weight, neighbourhood characteristics, socioeconomic factors, pregnancy, small-area analysis
Résumé
Contexte
À ce jour, la majorité des travaux de recherche portant sur le faible poids à la naissance s’intéresse davantage aux caractéristiques des mères, et moins à la façon dont se profile le risque lié à la mère (par le biais des facteurs contextuels). Cette étude vise à comprendre la façon dont les caractéristiques du milieu influent sur le faible poids à la naissance, de manière indépendante et en interaction avec des facteurs individuels, dans le contexte de milieux définis par la collectivité.
Méthode
La population étudiée comprenait toutes les naissances d’enfants uniques issus de mères résidant à Saskatoon; la période à l’étude était de trois ans (1992-1995; n=8504). Les données considérées étaient les caractéristiques de la mère/du père de l’enfant ainsi que six caractéristiques du milieu: désavantage socioéconomique, rupture sociale, condition physique, densité de la population, disponibilité et accessibilité des programmes et des services locaux et la prévalence du tabagisme. Une modélisation à niveaux multiples pour des résultats exprimés de façon binaire (faible poids à la naissance) a été utilisée; des rapports de cotes ainsi que des intervalles de confiance à 95 % se rapportant au modèle final ont été signalés.
Résultats
Les nouveaux-nés des familles bénéficiaires de l’aide sociale, issus d’une mère âgée de plus de 40 ans dont la mère a fait des fausses couches, étaient plus susceptibles d’avoir un faible poids à la naissance; cependant, les mères ayant eu plus d’une naissance d’enfant vivant étaient moins susceptibles d’avoir un enfant de faible poids à la naissance. Indépendamment des facteurs de risque individuels, les nourrissons se trouvant en milieu désavantagé sur le plan socioéconomique étaient plus susceptibles d’avoir un faible poids à la naissance (r.c. 1,34; i.c. 95 % 1,07; 1,68). Fait intéressant, le risque d’un faible poids à la naissance chez les nourrissons nés de mères seules était exacerbé par un degré plus élevé de rupture sociale du milieu. Les milieux comportant un faible degré de rupture sociale représentent un moindre risque de faible poids à la naissance pour les mères seules (r.c.=0,89; i.c. 95 % 0,72; 1,17) en les comparant aux milieux comportant un degré élevé de rupture sociale (r.c.=1,57; i.c. 95 % 1,18; 1,93).
Conclusion
Les facteurs contextuels du milieu influent directement sur le risque de faible poids à la naissance par des effets indépendants, de même qu’en atténuant le risque des facteurs individuels. Des études examinant simultanément les effets individuels et contextuels sur le poids à la naissance pourraient fournir un fondement plus solide à l’appui des points d’intervention multiples visant des personnes, de même que des milieux.
Mots clés: nourrisson, faible poids à la naissance, caractéristiques du lieu de résidence, facteurs socioéconomiques, grossesse, analyse régionale
Footnotes
Acknowledgements: The authors acknowledge the financial contribution of Canadian Population Health Initiative-CIHI, and thank colleagues in the Saskatchewan Ministry of Health, the Planning Department, City of Saskatoon, and the Saskatoon Health Region for sharing data. This study is based in part on non-identifiable data. The interpretations and conclusions contained herein do not necessarily represent those of the Government of Saskatchewan or Ministry of Health.
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