ORs for preterm birth among non-asthmatic and asthmatic mothers per 10 μg/m3 increase in the first trimester O3 levels
| Group | OR | 95% CI | OR* | 95% CI* | |
|---|---|---|---|---|---|
| O3 unadjusted model | Non-asthmatic | 1.03 | 1.01 to 1.05 | 1.03 | 1.00 to 1.05 |
| O3 unadjusted model | Asthmatic | 1.07 | 1.01 to 1.14 | 1.09 | 1.02 to 1.16 |
| O3 model 2† | Non-asthmatic | 1.04 | 1.00 to 1.08 | 1.08 | 1.02 to 1.15 |
| O3 model 2† | Asthmatic | 1.08 | 1.01 to 1.15 | 1.14 | 1.05 to 1.24 |
| O3 model 3‡ | Non-asthmatic | 1.04 | 1.00 to 1.08 | 1.06 | 1.01 to 1.11 |
| O3 model 3‡ | Asthmatic | 1.08 | 1.01 to 1.15 | 1.12 | 1.04 to 1.21 |
| O3 model 4§ | Non-asthmatic | 1.05 | 0.99 to 1.11 | 1.11 | 1.01 to 1.21 |
| O3 model 4§ | Asthmatic | 1.08 | 1.00 to 1.17 | 1.16 | 1.04 to 1.29 |
| O3 model 5¶ | Non-asthmatic | 1.04 | 0.98 to 1.10 | 1.07 | 0.99 to 1.15 |
| O3 model 5¶ | Asthmatic | 1.04 | 0.96 to 1.14 | 1.09 | 0.98 to 1.20 |
*Elective caesarean section excluded from the analysis.
†Adjusted for maternal age, parity, level of education, area of origin, maternal asthma, conception year and season of conception.
‡Adjusted for † and first trimester NOx.
§Adjusted for † and ‡ and first trimester temperature and relative humidity.
¶Adjusted for †–§, maternal smoking, family situation and BMI at the first antenatal care visit.