Table 2 Adjusted odds ratios (95% credible intervals) for predictors of preterm birth
Characteristics | Hierarchical logistic regression | Conditional logistic regression |
|---|---|---|
Physical exercise frequency per week (Reference: zero) | ||
 1–2 | 0.80 (0.68–0.92) | 0.85 (0.75–0.97) |
 3–4 | 0.70 (0.60–0.82) | 0.80 (0.70–0.91) |
  ≥ 5 | 0.68 (0.59–0.78) | 0.80 (0.71–0.89) |
 Doctors suggested not to | 2.50 (1.70–3.70) | 1.53 (1.20–1.94) |
Maternal age, years (Reference: 25 to < 30 years) | ||
  < 20 years | 1.68 (1.43–1.98) | 1.38 (1.20–1.57) |
 20 to < 25 years | 1.16 (1.02–1.31) | 1.12 (1.01–1.25) |
  ≥ 30 years | 1.27 (0.97–1.65) | 1.12 (0.91–1.39) |
Education (Reference: less than high school) | ||
 High school or occupational school | 0.97 (0.83–1.14) | 0.98 (0.86–1.12) |
 College | 1.14 (0.97–1.35) | 1.06 (0.93–1.21) |
 Graduate school | 0.97 (0.72–1.28) | 0.92 (0.73–1.17) |
Income (Reference: middle income, 3000–6999 RMB) | ||
 Low income (< 3000 RMB) | 1.22 (1.01–1.46) | 1.15 (0.99–1.33) |
 High income (≥7000 RMB) | 1.05 (0.93–1.20) | 1.02 (0.91–1.13) |
Family history | 2.28 (1.78–2.91) | 1.48 (1.25–1.76) |
Neonatal gender: male | 1.28 (1.16–1.43) | 1.16 (1.06–1.27) |
Parity: more than one | 0.96 (0.82–1.13) | 0.97 (0.85–1.10) |
BMI prior to pregnancy (Reference: normal weight) | ||
 Underweight | 1.03 (0.90–1.17) | 1.00 (0.90–1.12) |
 Overweight/Obesity | 1.00 (0.80–1.25) | 0.98 (0.82–1.17) |
Weight gain (per one kilogram increase) | 0.96 (0.94–0.97) | 0.97 (0.96–0.98) |
Maternal comorbidity | 1.71 (1.41–2.07) | 1.33 (1.15–1.54) |
Anemia | 0.97 (0.81–1.15) | 0.98 (0.85–1.13) |
Colporrhagia | 1.87 (1.66–2.10) | 1.43 (1.30–1.57) |
Indoor air pollution | 0.97 (0.84–1.11) | 0.99 (0.88–1.11) |