Table 5.
Risks of preterm birth at 75th and 95th percentiles of air pollution against the minimum preterm birth concentration of air pollution (threshold) by level of demographic factors.
| Factors | NO2 [OR (95% CI)] | SO2 [OR (95% CI)] | CO [OR (95% CI)] |
|---|---|---|---|
| Maternal age (years) | |||
| < 35 | |||
| 75th vs. threshold | 1.00 (0.99, 1.01) | 1.06 (0.95, 1.17) | 1.12 (0.94, 1.33) |
| 95th vs. threshold | 1.26 (1.09, 1.47) | 1.01 (0.97, 1.05) | 1.30 (1.05, 1.61) |
| ≥ 35 | |||
| 75th vs. threshold | 1.01 (0.97, 1.06) | 1.03 (0.98, 1.08) | 1.09 (0.99, 1.20) |
| 95th vs. threshold | 1.14 (1.03, 1.27) | 1.02 (0.99, 1.05) | 1.14 (1.01, 1.30) |
| Prepregnancy medical conditions | |||
| No | |||
| 75th vs. threshold | 1.01 (0.99, 1.02) | 1.04 (0.99, 1.10) | 1.12 (1.02, 1.24) |
| 95th vs. threshold | 1.18 (1.07, 1.30) | 1.01 (0.99, 1.03) | 1.24 (1.09, 1.41) |
| Yes | |||
| 75th vs. threshold | 1.67 (1.07, 2.61) | 1.02 (0.95, 1.10) | 1.11 (0.47, 2.59) |
| 95th vs. threshold | 1.90 (1.18, 3.04) | 1.03 (0.97, 1.09) | 1.11 (0.51, 2.40) |
| Previous pregnancy | |||
| 0 | |||
| 75th vs. threshold | 1.00 (0.99, 1.01) | 1.10 (1.00, 1.22) | 1.02 (0.93, 1.13) |
| 95th vs. threshold | 1.06 (0.93, 1.21) | 1.00 (0.99, 1.01) | 1.09 (0.93, 1.26) |
| ≥ 1 | |||
| 75th vs. threshold | 1.01 (0.99, 1.04) | 1.01 (0.97, 1.05) | 1.15 (1.03, 1.29) |
| 95th vs. threshold | 1.24 (1.12, 1.37) | 1.03 (0.99, 1.08) | 1.25 (1.09, 1.44) |
| Smoking | |||
| Yes | |||
| 75th vs. threshold | 2.02 (1.05, 3.89) | 1.08 (0.95, 1.24) | 2.35 (0.58, 9.63) |
| 95th vs. threshold | 2.59 (1.28, 5.25) | 1.04 (0.97, 1.11) | 2.47 (0.69, 8.82) |
| No | |||
| 75th vs. threshold | 1.01 (0.99, 1.03) | 1.03 (0.98, 1.08) | 1.06 (0.98, 1.15) |
| 95th vs. threshold | 1.16 (1.06, 1.27) | 1.01 (0.99, 1.04) | 1.15 (1.03, 1.28) |
| Number of births | |||
| Single | |||
| 75th vs. threshold | 1.00 (0.99, 1.01) | 1.07 (0.99, 1.15) | 1.09 (0.98, 1.21) |
| 95th vs. threshold | 1.12 (1.02, 1.23) | 1.00 (1.00, 1.00) | 1.14 (1.00, 1.30) |
| Multiple | |||
| 75th vs. threshold | 1.03 (0.96, 1.10) | 1.01 (0.97, 1.04) | 1.11 (0.95, 1.28) |
| 95th vs. threshold | 1.32 (1.12, 1.55) | 1.10 (1.01, 1.19) | 1.28 (1.06, 1.55) |
| Infant sex | |||
| Female | |||
| 75th vs. threshold | 1.01 (0.98, 1.05) | 1.01 (0.96, 1.05) | 1.16 (1.00, 1.34) |
| 95th vs. threshold | 1.20 (1.06, 1.36) | 1.02 (0.97, 1.08) | 1.26 (1.06, 1.49) |
| Male | |||
| 75th vs. threshold | 1.00 (0.99, 1.02) | 1.07 (1.00, 1.14) | 1.06 (0.96, 1.17) |
| 95th vs. threshold | 1.15 (1.03, 1.28) | 1.01 (0.99, 1.04) | 1.14 (1.00, 1.30) |
| SES index | |||
| Index 1–5 | |||
| 75th vs. threshold | 1.02 (0.99, 1.05) | 1.05 (0.95, 1.17) | 3.25 (1.72, 6.15) |
| 95th vs. threshold | 1.19 (0.96, 1.46) | 1.05 (0.98, 1.13) | 3.27 (1.70, 6.27) |
| Index 6–10 | |||
| 75th vs. threshold | 1.01 (0.99, 1.04) | 1.03 (0.98, 1.09) | 1.08 (0.99, 1.17) |
| 95th vs. threshold | 1.18 (1.07, 1.29) | 1.01 (0.99, 1.03) | 1.17 (1.05, 1.30) |
| Abbreviations: CI, confidence interval; CO, carbon monoxide (mean of 0–24 hr preceding onset of labor); NO2, nitrogen dioxide (mean of 0–24 hr preceding onset of labor); OR, odds ratio; SO2, sulfur dioxide (mean of 24–48 hr preceding onset of labor). p-Values for differences are presented in Table S3. | |||