Table 3.
HRs (95% CIs) of the extreme temperature exposure (Model Ia) for PTB according to maternal pre-pregnancy status of BMI.
| BMI status | Gestational period | Low temperature | High temperature |
|---|---|---|---|
| Normal weight | 1st trimester | 0.881 (0.812, 0.955) | 1.449 (1.317, 1.593) |
| 2nd trimester | 0.763 (0.694, 0.839) | 1.326 (1.222, 1.438) | |
| 3rd trimester | 1.512 (1.359, 1.682) | 1.761 (1.621, 1.912) | |
| Underweight | 1st trimester | 1.045 (0.917, 1.191) | 1.449 (1.241, 1.692) |
| 2nd trimester | 0.865 (0.741, 1.008) | 1.146 (1.002, 1.311) | |
| 3rd trimester | 1.825 (1.529, 2.179) | 1.784 (1.559, 2.042) | |
| Overweight or Obesity | 1st trimester | 0.936 (0.771, 1.136) | 1.077 (0.865, 1.341) |
| 2nd trimester | 0.793 (0.636, 0.989) | 1.233 (1.020, 1.491) | |
| 3rd trimester | 1.411 (1.104, 1.803) | 1.825 (1.502, 2.218) |
a
Model I: 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 (preterm birth, 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 PM2.5, O3, NO2 and SO2).