Table 2 shows the demographic characteristics of eligible children stratified by LBW status. LBW children were more likely to be girls, be premature, be the first-born baby, have smoking mothers, have mothers for individual and municipality-level variables simultaneously, this did not substantially change the point estimates. In the fully adjusted models, adjusted ORs following one IQR increase in each pollutant were 1.09 (95% CI: 1.00, 1.19) for SPM, 1.11 (95% CI: 0.99, 1.26) for NO2, and 1.71 (95% CI: 1.18, 2.46) for SO2.