Characteristic | Model 1 adjusted for year of birth | Model 2 adjusted for individual level confounders | Model 3 adjusted for municipality level confounders | Model 4 adjusted for model 2 (except smoking) and Model 3 | Model 5 adjusted for model 2 and model 3 |
---|---|---|---|---|---|
OR (95% CI) | aOR (95% CI) | aOR (95% CI) | aOR (95% CI) | aOR (95% CI) | |
Year of birth | 1.01 (1.00-1.02) | 1.01 (1.00-1.02) | 1.01 (1.00-1.02) | 1.01 (1.00-1.02) | |
Maternal age, years (per one year increase) | 1.03 (1.03-1.04) | 1.02 (1.02-1.03 | 1.03 (1.03-1.04) | ||
Parity | |||||
Nulliparous women | 1 | 1 | 1 | ||
Multiparous women | 0.27 (0.26-0.28) | 0.27 (0.26-0.28) | 0.27 (0.25-0.28) | ||
Prior preterm birth | 2.14 (1.96-2.34) | 2.20 (2.01-2.40) | 2.14 (1.96-2.34) | ||
Smoking status | |||||
Non-smoking | 1 | 1 | |||
Quit smoking during 1st trimester | 0.96 (0.88-1.05) | 0.96 (0.88-1.05) | |||
Smoking after 1st trimester | 2.47 (2.35-2.59) | 2.45 (2.34-2.57) | |||
Missing information | 1.34 (1.19-1.49) | 1.32 (1.18-1.48) | |||
Socioeconomic status | |||||
Upper white collar workers | 1 | 1 | 1 | ||
Lower white collar workers | 1.179 (1.09-1.26) | 1.22 (1.13-1.31) | 1.16 (1.08-1.25) | ||
Blue collar workers | 1.21 (1.11-1.32) | 1.39 (1.28-1.51) | 1.20 (1.10-1.30) | ||
Othersa | 1.17 (1.09-1.27) | 1.23 (1.14-1.32) | 1.17 (1.08-1.26) | ||
Missing information | 1.19 (1.10-1.29) | 1.29 (1.20-1.40) | 1.20 (1.111.29) | ||
Municipality derivation class b | |||||
Education | |||||
High (least deprived) | 1 | 1 | 1 | ||
Intermediate | 1.09 (1.03-1.14) | 1.07 (1.01-1.13) | 1.03 (0.98-1.09) | ||
Low (most deprived) | 1.12 (1.04-1.20) | 1.11 (1.03-1.19) | 1.05 (0.97-1.13) | ||
Income | |||||
High (least deprived) | 1 | 1 | 1 | ||
Intermediate | 0.94 (0.88-0.99) | 0.93 (0.87-0.99) | 0.94 (0.89-1.00) | ||
Low (most deprived) | 0.99 (0.92-1.07) | 0.99 (0.92-1.07) | 1.01 (0.94-1.09) | ||
Unemployment | |||||
Low (least deprived) | 1 | 1 | 1 | ||
Intermediate | 1.03 (0.98-1.09) | 1.07 (1.01-1.12) | 1.06 (1.01-1.12) | ||
High (most deprived) | 1.12 (1.06-1.19) | 1.15 (1.08-1.22) | 1.13 (1.06-1.20) | ||
Log (population) | 1.06 (1.04-1.08) | 1.01 (1.00-1.03) | 1.01 (0.99-1.03) |