BMC Public Health 2009, 9:237 http://www.biomedcentral.com/1471-2458/9/237 Table 3: Crude and adjusted associations between area characteristics and adverse birth outcomes, singleton births, Québec, Canada, 1999–2003 Crude OR 95% CI Adjusted OR* 95% CI Adjusted OR† 95% CI 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 1.13‡ 1.08‡ Referent 1.07‡ 0.99‡ Referent 0.92 0.94 Referent 1.21‡ 1.12‡ Referent 0.91‡ 0.89‡ Referent 0.95 1.00 Referent 1.07–1.20 1.02–1.14 1.01–1.14 0.94–1.06 0.86–0.98 0.89–1.00 1.14–1.29 1.05–1.19 0.85–0.98 0.83–0.95 0.89–1.02 0.93–1.07 1.06‡ 1.04‡ Referent 1.11‡ 1.03‡ Referent 0.96‡ 0.96‡ Referent 1.09‡ 1.05‡ Referent 0.97 0.98 Referent 0.96 0.98 Referent 1.01–1.12 0.99–1.10 1.05–1.17 0.98–1.08 0.90–1.01 0.91–1.01 1.03–1.14 1.00–1.10 0.92–1.03 (0.92–1.05) 0.90–1.01 0.93–1.03 1.05 1.02 Referent 1.10 1.04 Referent 1.01 0.99 Referent 1.09‡ 1.06‡ Referent 0.94‡ 0.99‡ Referent 0.94‡ 0.96‡ Referent 0.98–1.12 0.96–1.09 1.02–1.18 0.97–1.12 0.94–1.09 0.93–1.05 1.03–1.15 1.00–1.12 0.88–1.00 0.94–1.05 0.88–1.00 0.90–1.01 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. Discussion This study examines, in a Canadian setting, associations between area income, immigrant density, and income inequality in relation to PTB and SGA birth. Previous stud- ies have not considered the joint influence of these neigh- bourhood characteristics. We build on and extend previous research documenting interactions between area context and race [5,6,8,15,17,18,20,21,23]. Our results indicate that, independent of individual maternal charac- teristics, the influence of area context varies according to different social markers. Our results are consistent with studies demonstrating an adverse influence of high area deprivation on PTB [1-6,8] and SGA birth [3-5]. Though area poverty was in our study more strongly associated with SGA birth than PTB, this finding was not observed in another study evaluating these same two birth outcomes [5]. The literature suggests PTB may be related to stress, possibly to a greater extent than SGA birth [44,45], while SGA birth may be more strongly related to lifestyle factors such as tobacco use [46,47]. Thus, the stronger associations with SGA birth may be related to the lower material/social resources present in deprived neighbourhoods, which may predis- pose less favourable behaviours among mothers. Our stratified analyses indicated that area poverty was more strongly associated with SGA birth among mothers with low compared to high education, this finding possibly being due to a greater level of unfavourable health-related behaviours in socio-economically vulnerable populations [48]. Our stratified analyses also indicated that area pov- erty was associated with PTB and SGA birth among Cana- dian-born but not foreign-born mothers. A separate study reported an association between area income and both PTB and full-term low birthweight (a proxy for SGA birth) among long-term residents but not recent immigrants of Toronto, Canada [7], in line with our findings. Foreign- born mothers, potentially healthier because of the selec- tive process of immigration [7,49], may be more resilient than native-born populations to area deprivation. Other studies evaluating the influence of area disadvantage according to race (not maternal birth place) have not yielded consistent results [5,6]. Page 6 of 11 (page number not for citation purposes)