BMC Public Health 2009, 9:237 http://www.biomedcentral.com/1471-2458/9/237 Table 1: Frequency of preterm and small-for-gestational age birth according to individual- and area-level characteristics, singleton births, Québec, Canada, 1999–2003 % PTB N* SGA birth % N* Individual-level characteristics Maternal birth place Foreign-born Canadian-born Maternal education No high school diploma High school diploma Some post secondary Some university or more Maternal age <20 years 20–34 years 35+ years Civil status Married Cohabiting Single Previous births None One or more Infant sex Male Female Area-level characteristics Income Poorest Intermediate Wealthiest Immigrant density Low Intermediate High Income inequality High Intermediate Low Total 6.3 59 474 6.3 291 149 8.3 41 558 7.3 35 473 6.3 67 391 5.4 183 041 8.8 6.1 7.0 14 236 289 745 49 025 5.7 146 691 6.4 172 401 8.9 24 870 6.7 181 422 5.9 171 584 6.7 114 187 6.4 119 311 5.9 119 508 6.6 115 375 6.2 119 046 6.2 118 585 6.1 117 485 6.3 118 209 6.6 117 312 6.3 353 006 9.5 8.1 12.0 10.0 8.9 6.8 11.7 8.1 8.6 7.3 8.6 11.8 8.4 8.3 9.0 8.4 7.6 8.1 8.0 8.9 59 432 290 922 41 528 35 450 67 343 182 918 14 222 289 529 48 976 146 590 172 268 24 840 181 279 171 448 114 076 119 223 119 428 115 287 118 956 118 484 8.1 117 386 8.3 118 120 8.5 117 221 8.3† 352 727 7.2 167 749 10.4 167 613 5.5 185 257 6.5 185 114 PTB = preterm birth; SGA = small-for-gestational-age * Denominators do not sum to total because missing data are not shown. † The overall prevalence of SGA birth has declined in Québec in the past decade, which explains the 8.3% prevalence rather than the expected 10% (the SGA reference curves were constructed for 1994–1996 at a time when SGA birth was more common)[31]. Higher area poverty was associated with progressively higher proportions PTB and SGA birth for most social markers (i.e., foreign-born, native-born, lesser education, higher education, Table 2). A statistically non-significant exception was the trend for PTB among foreign-born mothers. Greater immigrant density was negatively associated with PTB except among foreign-born mothers, for whom the relationship was positive (Table 2). For SGA birth, a pat- tern was observed among foreign-born mothers and mothers with higher education (greater immigrant den- sity was associated with progressively higher proportions SGA birth). Income inequality was inversely associated with PTB and SGA birth for most social markers, with the exception of PTB among foreign-born mothers and SGA birth among mothers with higher education (Table 2). A less pro- nounced trend (P-value = 0.03) for income inequality and SGA birth was present among mothers with lesser educa- tion. Non-stratified regression models All area variables were associated with PTB in unadjusted models (Table 3). Relative to opposite tertiles, higher odds of PTB were found for high area poverty (OR 1.13, 95% CI 1.07–1.20) and low immigrant density (OR 1.07, 95% CI 1.01–1.14). Lower odds of PTB were found for high income inequality (OR 0.92, 95% CI 0.86–0.98). Associations remained after adjustment for individual- level variables, with the exception of income inequality (OR 0.96, 95% CI 0.90–1.01). In fully adjusted models (accounting for all three area variables), only immigrant density remained statistically significant (OR 1.10, 95% CI 1.02–1.18). Unadjusted models indicated greater odds of SGA birth for high area poverty (OR 1.21, 95% CI 1.14–1.29), lower odds for low immigrant density (OR 0.91, 95% CI 0.85– 0.98), and no association for high income inequality (OR 0.95, 95% CI 0.89–1.02), relative to the opposite tertile (Table 3). Upon adjustment for individual and area varia- bles, the strength of associations with SGA birth dimin- ished for area poverty (OR 1.09, 95% CI 1.03–1.15) and immigrant density (OR 0.94, 95% CI 0.88–1.00), but remained stable for income inequality (OR 0.94, 95% CI 0.88–1.00). Regression models stratified by maternal birth place Among native born-mothers, high area poverty (OR 1.07, 95% CI 1.00–1.14) and low immigrant density (OR 1.14, 95% CI 1.07–1.21), but not income inequality (OR 1.02, 95% CI 0.95–1.09), were associated with PTB in the fully adjusted model (Table 4). Income inequality was none- theless associated with PTB among native-born mothers in the model adjusted for individual-level variables only (OR 0.92, 95% CI 0.86–0.98). Among foreign-born mothers, only immigrant density was associated with PTB in the fully adjusted model (OR 0.79, 95% CI 0.63–1.00), with odds in the opposite direction than those of native- born mothers. Page 4 of 11 (page number not for citation purposes)