Table 4.
Comparison of spontaneous preterm birth odds ratio (95% CI) with medically indicated preterm birth and all preterm birth odds ratio (95% CI) for PM2.5 (per 10 μg/m3) and NO2 (per 20 ppb) using estimated overall exposures in unadjusted and adjusted models.
| Pollutant | Exposure trimester | Model | Spontaneous preterm births | Medically indicated preterm births | All preterm births |
|---|---|---|---|---|---|
| PM2.5 | 1st | Crude | 0.87 (0.81, 0.94) | 0.81 (0.73, 0.89) | 0.85 (0.80, 0.90) |
| 1st | Fully adjusted | 0.99 (0.90, 1.08) | 0.94 (0.84, 1.06) | 0.97 (0.90,1.05) | |
| 2nd | Crude | 0.85 (0.78, 0.91) | 0.80 (0.73, 0.89) | 0.83 (0.78, 0.88) | |
| 2nd | Fully adjusted | 0.99 (0.90, 1.09) | 0.95 (0.84, 1.08) | 0.95 (0.88, 1.03) | |
| NO2 | 1st | Crude | 0.83 (0.78, 0.88) | 0.77 (0.71, 0.84) | 0.81 (0.77, 0.85) |
| 1st | Fully adjusted | 0.94 (0.87, 1.02) | 0.90 (0.81, 0.99) | 0.92 (0.87, 0.98) | |
| 2nd | Crude | 0.81 (0.77, 0.86) | 0.78 (0.72, 0.84) | 0.80 (0.76, 0.84) | |
| 2nd | Fully adjusted | 0.90 (0.83, 0.97) | 0.89 (0.80, 0.99) | 0.89 (0.83, 0.95) | |
| Abbreviations: PM2.5, particulate matter ≤ 2.5 μm in aerodynamic diameter; μg/m3, micrograms per cubic meter; NO2, nitrogen dioxide; ppb, parts per billion. All term births serve as the reference outcome. | |||||