Table 2.
Fraction and number of preterm births attributable to extreme heat.
| Subgroup | Fraction of Preterm Births % (empirical CI) | Number of Preterm Births per Million Pregnancies No. (empirical CI) |
|---|---|---|
| All US | 0.17 (0.14, 0.19) | 154 (127, 173) |
| Geographic Region | ||
| Northeast | 0.13 (0.08, 0.17) | 116 (73, 153) |
| Southeast | 0.17 (0.13, 0.20) | 181 (141, 219) |
| Midwest | 0.19 (0.13, 0.23) | 176 (122, 220) |
| Great Plains | 0.14 (0.05, 0.21) | 140 (50, 216) |
| Northwest | 0.12 (0.01, 0.22) | 90 (10, 160) |
| Southwest | 0.20 (0.12, 0.26) | 174 (108, 222) |
| Climate Zone | ||
| Hot-Humid | 0.14 (0.09, 0.19) | 151 (93, 206) |
| Mixed-Humid | 0.14 (0.10, 0.18) | 145 (99, 185) |
| Hot-Dry/Mixed-Dry | 0.21 (0.13, 0.29) | 194 (113, 262) |
| Cold/Very Cold | 0.18 (0.14, 0.22) | 158 (122, 189) |
| Marine | 0.09 (0.01, 0.16) | 69 (7, 122) |
Abbreviations: CI, confidence interval.
Extreme heat was defined as temperatures above 95th percentile of county-specific temperature distributions.