Table 2. Descriptive Statistics of Heat and Green Space Exposures During the Entire Pregnancy for the Study Population Based on SMM Status, 2008 to 2018.
| Total pregnancies (N = 403 602) | Non-SMM (n = 396 504) | SMM21 (n = 7098) | SMM20 (n = 3446) | SMMcardio (n = 684) | |
|---|---|---|---|---|---|
| Proportions of heat days, median (IQR), % | |||||
| HD_P75 | 3.93 (0.73-11.07) | 3.94 (0.73-11.11) | 3.52 (0.72-10.83) | 4.00 (0.74-11.91) | 3.99 (0.72-13.60) |
| HD_P90 | 0.72 (0.00-2.87) | 0.72 (0.00-2.87) | 0.71 (0.00-2.87) | 0.75 (0.00-3.24) | 0.74 (0.00-3.92) |
| HD_P95 | 0.00 (0.00-1.06) | 0.00 (0.00-1.06) | 0.00 (0.00-1.07) | 0.00 (0.00-1.24) | 0.35 (0.00-1.41) |
| Green space exposure, mean (SD), % | |||||
| Total green space | 25.24 (4.09) | 25.24 (4.09) | 25.26 (4.16) | 25.17 (4.14) | 24.98 (3.91) |
| Trees | 15.34 (4.22) | 15.34 (4.22) | 15.37 (4.25) | 15.20 (4.34) | 15.02 (4.21) |
| Low-lying vegetation | 4.58 (1.46) | 4.58 (1.46) | 4.59 (1.46) | 4.59 (1.44) | 4.57 (1.44) |
| Grass | 5.33 (1.48) | 5.33 (1.48) | 5.31 (1.48) | 5.37 (1.52) | 5.39 (1.62) |
| Missing, No. (%) | 1026 (0.25) | 998 (0.25) | 28 (0.39) | 20 (0.58) | 4 (0.58) |
Abbreviations: HD_P75, moderate heat days exceeding the 75th daily maximum temperature percentile; HD_P90, high heat days exceeding the 90th daily maximum temperature percentile; HD_P95, extreme heat days exceeding the 95th daily maximum temperature percentile; SMM, severe maternal morbidity; SMM20, SMM measured without the blood product transfusion; SMM21, SMM measured with all 21 indicators; SMMcardio, the cardiovascular-related subcategory in SMM.