Figure 1.

Hazard ratios (and 95% confidence intervals) of PTB associated with mean daily temperature during three trimesters of pregnancy across normal weight, underweight, overweight or obese women. Models were adjusted for characteristics of maternal age (<25 years, 25 ~ 34 years and ≥ 35 years), delivery mode (vaginal delivery and cesarean section), newborn gender (male and female), history of adverse pregnancy outcomes (PTB, miscarriage, induced abortion and stillbirth), active smoking, husband smoke and alcohol drinking status during early stage of pregnancy, season of delivery (spring, summer, fall and winter), mean of relative humidity and air pollutants (including PM_2.5, O₃, NO₂ and SO₂).