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Table 3 Crude and adjusted odds ratios (OR) and for premature birth by pollution exposure

From: Maternal exposure to low-level air pollution and pregnancy outcomes: a population-based study

Exposure Crude odds ratio Adjusted* odds ratio
  OR (95%CI) OR (95%CI)
Formaldehyde Categorical variable (tertiles)
1 (reference)   
2 0.98 (0.68–1.40) 1.11 (0.72–1.71)
3 1.16 (0.82–1.63) 1.37 (0.91–2.05)
Continuous variable (per 5 μg/m3 increase in concentration)
  1.03 (0.76–1.40) 1.07 (0.77–1.49)
Nitrogen dioxide Categorical variable (tertiles)
1 (reference)   
2 1.01 (0.70–1.46) 1.14 (0.77–1.68)
3 1.40 (0.99–1.98) 1.68 (1.15–2.46)
Continuous variable (per 10 μg/m3 increase in concentration)
  1.16 (1.01–1.34) 1.25 (1.07–1.46)
  1. * Adjusted for parity, maternal age (≤ 19, 20–29, 30–34, ≥ 35), marital status, education, season of birth, maternal and paternal smoking