Table 4.
Fraction and number of preterm births attributable to extreme temperatures.
| Pre-pregnancy BMI categories | Trimester | Low temperaturea | High temperaturea | ||
|---|---|---|---|---|---|
| Attributable number | Attributable fraction (%) | Attributable number | Attributable fraction (%) | ||
| Normal weight | 1 | −72 (−114,-27) | −0.63 (−1,-0.24) | 263 (186,347) | 2.31 (1.63,3.05) |
| 2 | −311 (−401,-211) | −2.74 (−3.54,-1.86) | 223 (152,300) | 2.08 (1.42,2.79) | |
| 3 | 482 (338,642) | 4.18 (2.93,5.56) | 351 (286,420) | 3.17 (2.58,3.79) | |
| Underweight | 1 | 4 (−8,17) | 0.19 (−0.35,0.81) | 49 (26,75) | 2.26 (1.21,3.48) |
| 2 | −28 (−54,2) | −1.33 (−2.56,0.08) | 18 (0,39) | 0.91 (0.01,1.93) | |
| 3 | 121 (78,174) | 5.59 (3.58,7.98) | 66 (47,88) | 3.14 (2.24,4.18) | |
| Overweight or obese | 1 | −6 (−21,12) | −0.27 (−0.97,0.58) | 8 (−15,37) | 0.39 (−0.68,1.72) |
| 2 | −43 (−76,-2) | −2.05 (−3.6,-0.11) | 29 (3,62) | 1.45 (0.12,3.05) | |
| 3 | 61 (15,118) | 2.78 (0.7,5.44) | 69 (42,103) | 3.31 (2.01,4.88) | |
a
High temperatures were defined as temperatures above the 95th percentile, and low temperatures were defined as temperatures below the 5th percentile, based on the distribution of daily mean air temperature exposures throughout each trimester.