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Table 2 Adjusted odds ratios (95% credible intervals) for predictors of preterm birth

From: Association between maternal outdoor physical exercise and the risk of preterm birth: a case-control study in Wuhan, China

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)
  1. Maternal comorbidity includes any of the following comorbidities: diabetes, thyroid disease, hepatitis, hypertension, heart disease, renal disease, epilepsy, asthma, depression, anxiety, or others