BMC Public Health 2009, 9:237 http://www.biomedcentral.com/1471-2458/9/237 Table 5: Adjusted associations between area characteristics and adverse birth outcomes according to maternal education, singleton births, Québec, Canada, 1999–2003* PTB Area income Poorest Intermediate Wealthiest Immigrant density Low Intermediate High Income inequality High Intermediate Low SGA birth Area income Poorest Intermediate Wealthiest Immigrant density Low Intermediate High Income inequality High Intermediate Low OR† 1.08 1.07 Referent 1.02 0.99 Referent 0.94 1.01 Referent 1.09 1.05 Referent 0.95 1.02 Referent 0.96 0.98 Referent High school diploma or less 95% CI OR‡ 95% CI OR† Some postsecondary or more 95% CI OR‡ 95% CI 0.99–1.18 0.98–1.18 0.93–1.12 0.90–1.09 0.86–1.03 0.94–1.10 1.00–1.19 0.96–1.14 0.87–1.04 0.93–1.12 0.88–1.05 0.90–1.06 1.08 1.08 Referent 1.01 1.01 Referent 0.96 1.03 Referent 1.13 1.09 Referent 0.90 1.04 Referent 0.92 0.94 Referent 0.97–1.19 0.97–1.19 0.90–1.12 0.90–1.12 0.86–1.08 0.94–1.13 1.02–1.24 0.99–1.20 0.81–0.99 0.94–1.15 0.83–1.03 0.86–1.03 1.04 1.02 Referent 1.16 1.07 0.92 0.92 Referent 1.08 1.05 Referent 1.00 0.97 Referent 0.94 0.98 Referent 0.97–1.12 0.95–1.09 1.08–1.24 1.10–1.15 0.86–0.99 0.86–0.98 1.03–1.14 1.00–1.11 0.94–1.05 0.91–1.03 0.89–0.99 0.93–1.03 1.02 0.99 Referent 1.15 1.08 Referent 1.00 0.97 Referent 1.07 1.05 Referent 0.95 0.97 Referent 0.93 0.97 Referent 0.95–1.10 0.92–1.07 1.06–1.25 1.00–1.17 0.92–1.09 0.90–1.04 1.00–1.13 0.99–1.11 0.89–1.02 0.91–1.04 0.87–1.00 0.92–1.03 PTB = preterm birth; SGA = small-for-gestational-age * All results are for multi-level logistic regression models. † Adjusted for individual-level variables (maternal age, education, civil status, birth place, and previous births). PTB is also adjusted for infant sex. ‡ Adjusted for individual-level variables and all variables in table complicates comparisons of studies is the wide spectrum of segregation measures that have been studied. However, when we compare our results to other studies that used a percentage-based indicator for segregation, results are still contradictory [5,15,17]. Thus, immigrant density in Québec may not be comparable to racial segregation in the United States. While non-stratified models suggested that immigrant density may be protective for PTB, its associations with SGA birth were unfavourable. Our findings are in line with research supporting an adverse influence of ethnic segre- gation on SGA birth [5,16,22]. Unlike PTB, however, strat- ified analyses did not support a differential influence according to education. Evidence for a contextual influence of income inequality was weaker than for area poverty and immigrant density, in line with research showing income inequality has a weaker influence in small areas compared to larger places [27]. Nevertheless, our results suggested an unexpectedly protective association, somewhat more for SGA birth than PTB. Protective associations between income inequality and adult outcomes have been observed by others [51- 54], but not for birth outcomes. The sparse research per- formed thus far on birth outcomes supports an adverse association between high income inequality and PTB [23,28] or low birthweight [26]. Income inequality in Québec may be a characteristic of affluent neighbour- hoods, affluence itself being associated with favourable birth outcomes [54]. Income inequality could also be a proxy for other unrelated neighbourhood factors favoura- bly associated with birth outcomes. We used the CV, an indicator sensitive to the upper ends of the income spec- trum [55], and associations could be different with indi- cators sensitive to other parts of the income spectrum. Two competing theories in the income inequality litera- ture may also be considered [23,56]. These include the "neo-materialist" pathway which posits that underinvest- ment in material capital in less equal communities trans- lates into lost opportunities and possible adoption of harmful health behaviours, and the "psychosocial" path- Page 8 of 11 (page number not for citation purposes)