Table 1 Characteristics of study participants (from gestational 20th week to 43rd week). Other characteristics were summarized in Supplemental Table S1
Characteristics | Subgroup | N (%) or mean (standard deviation, interquartile range [IQR]) |
|---|---|---|
Total | 47,845,444 (100.00) | |
Maternal age (years) | 27.3 (6.1, 23.0–32.0) | |
Fetal outcome | Fetal death | 316,875 (0.66) |
Livebirth | 47,528,569 (99.34) | |
Years of maternal education | ≤8 | 2,891,993 (6.04) |
9–12 | 21,854,907 (45.68) | |
13–16 | 17,025,390 (35.58) | |
17+ | 4,197,367 (8.77) | |
Unknown | 1,875,787 (3.92) | |
Previous pregnancy | Yes | 31,844,671 (66.56) |
No | 15,720,316 (32.86) | |
Unknown | 280,457 (0.59) | |
Maternal ethnicity | White | 36,708,200 (76.72) |
African American | 7,798,101 (16.30) | |
Others | 3,339,143 (6.98) | |
PM2.5 exposure (µg/m3) | Full gestational | 12.6 (4.1, 9.7–15.5) |
First trimester | 12.7 (4.5, 9.5–15.7) | |
Second trimester | 12.6 (4.3, 9.5–15.5) | |
Third trimester | 12.5 (4.4, 9.3–15.5) | |
Relative humidity (%) | 70.1 (12.9, 68.0–78.1) | |
Temperature (°C) | 14.1 (5.0, 10.2–17.5) | |
Wind speed (m/s) | 3.5 (0.6, 3.0–3.8) | |