BMC Public Health 2009, 9:237 http://www.biomedcentral.com/1471-2458/9/237 Table 4: Adjusted associations between area characteristics and adverse birth outcomes according to maternal birth place, 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* 0.96 0.96 Referent 0.80 0.91 Referent 1.05 0.97 Referent 1.02 0.95 Referent 0.98 0.95 Referent 0.95 0.94 Referent Foreign-born 95% CI OR† 95% CI OR* Canadian-born 95% CI OR† 0.85–1.09 0.85–1.09 0.65–0.99 0.81–1.03 0.92–1.21 0.84–1.12 0.92–1.14 0.85–1.06 0.83–1.16 0.85–1.06 0.84–1.07 0.82–1.06 0.95 0.95 Referent 0.79 0.89 Referent 0.98 0.93 Referent 1.00 0.93 Referent 0.96 0.93 Referent 0.94 0.93 Referent 0.83–1.09 0.83–1.08 0.63–1.00 0.77–1.02 0.84–1.15 0.79–1.08 0.88–1.13 0.83–1.05 0.80–1.16 0.83–1.05 0.82–1.09 0.81–1.06 1.07 1.04 Referent 1.12 1.05 Referent 0.92 0.96 Referent 1.11 1.06 Referent 0.98 0.99 Referent 0.95 0.99 Referent 1.02–1.13 0.98–1.11 1.06–1.19 0.99–1.12 0.86–0.98 0.90–1.01 1.05–1.17 1.00–1.13 0.92–1.04 0.93–1.06 0.90–1.01 0.94–1.05 1.07‡ 1.03‡ Referent 1.14‡ 1.08‡ Referent 1.02‡ 1.01‡ Referent 1.13 1.08 Referent 0.94 1.01 Referent 0.95 0.98 Referent 95% CI 1.00–1.14 0.97–1.09 1.07–1.21 1.02–1.15 0.95–1.09 0.96–1.07 1.06–1.20 1.02–1.15 0.88–1.01 0.95–1.08 0.88–1.02 0.92–1.04 PTB = preterm birth; SGA = small-for-gestational-age * 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. ‡ Results are for generalised estimating equations. All other results are for multi-level logistic regression models. We found a protective association between high immi- grant density and PTB, and the magnitude of the associa- tion was greater than for area poverty. This finding is in line with research documenting fewer adverse mental health outcomes in areas with higher minority popula- tions [50]. Stratified analyses, however, showed that high immigrant density was protective for PTB among Cana- dian-born mothers, but unfavourably associated with PTB among foreign-born mothers. This intriguing finding has not been previously reported. A study restricted to US Black mothers did, in comparison, find an elevated odds of PTB for racially concentrated neighbourhoods among mothers that were US-born but not those foreign-born [15]. The authors did not, however, account for neigh- bourhood income. Hence it is difficult to know the extent to which racial concentration may be a marker for poverty in the study. What can explain the interaction observed in our study? The stronger association with PTB than with SGA birth suggests that immigrant density may be operat- ing through stress mechanisms, assuming PTB is more strongly linked to stress [5]. Thus, high immigrant density may be associated with conditions that reduce stress in native-born mothers, but increase stress in foreign-born mothers. Such conditions might arise if, for example, employment opportunities were greater for native- than for foreign-born individuals due to prejudice or network integration. The immigrant composition of Québec, with ties to French-speaking source countries, might also be driving these results although the underlying pathways are unclear. We also found high immigrant density was associated with greater odds of PTB among mothers with high but not low education. Educated mothers might more readily access benefits conferred by high immigrant density (e.g., employment opportunities). Other studies, mainly focussing on segregation, have considered racial class but not education as a modifier of neighbourhood effects. Maternal education is generally treated as a control varia- ble and not as a potential modifier [17,18,20]. Studies are, however, unclear on whether ethnic segregation is protec- tive [16,19] or harmful [5,15-18] for PTB. An issue that Page 7 of 11 (page number not for citation purposes)