Table 1. Demographics of the birth cohort, including births from 23 October 2010 to 24 October 2019.
Limited to singletons, excluded implausible birthweight and gestation lengths, and those missing maternal zip code. General inclusion criteria: birthweight of >500 and <6800 g, birth week of >20 and <45, zip code provided, and singleton.
| Covariate | Category | Exposed Aliso communities | Los Angeles County | Matched control communities (tracts) | Statewide urban |
|---|---|---|---|---|---|
| 10-km buffer south of SS-25 | Excluding exposed | Excluding exposed | Excluding exposed | ||
| n = 13,848 | n = 1,056,901 | n = 20,196 | n = 3,812,896 | ||
| n (%) or means ± SD | n (%) or means ± SD | n (%) or means ± SD | n (%) or means ± SD | ||
| Maternal age | Means ± SD | 31.1 ± 5.6 | 29.6 ± 6.2 | 31.0 ± 5.5 | 29.5 ± 6.1 |
| <20 | 349 (2.5) | 57,658 (5.5) | 488 (2.4) | 198,914 (5.2) | |
| 20–25 | 1933 (14.0) | 230,905 (21.8) | 2729 (13.5) | 846,230 (22.2) | |
| 26–30 | 3726 (26.9) | 281,060 (26.6) | 5732 (28.4) | 1,059,926 (27.8) | |
| 31–35 | 4784 (34.5) | 294,809 (27.9) | 7056 (34.9) | 1,071,463 (28.1) | |
| 36+ | 3056 (22.1) | 192,461 (18.2) | 4190 (20.7) | 636,317 (16.7) | |
| Maternal race/ethnicity | Hispanic, any race | 5050 (36.5) | 598,383 (56.6) | 6215 (30.8) | 1,812,731 (47.5) |
| White, non-Hispanic | 5003 (36.1) | 197,266 (18.7) | 10,923 (54.1) | 1,027,095 (26.9) | |
| Black, non-Hispanic | 602 (4.3) | 77,199 (7.3) | 209 (1.0) | 220,158 (5.8) | |
| Asian/Pacific Islander, non-Hispanic | 2905 (21) | 165,169 (15.6) | 2499 (12.4) | 623,026 (16.3) | |
| Other/unknown | 288 (2.1) | 18,884 (1.8) | 350 (1.7) | 129,886 (3.4) | |
| Maternal education | Mean of ordinal ranks (0–8)* | 5.1 ± 1.8 | 4.2 ± 2 | 5.0 ± 1.9 | 4.4 ± 2 |
| Baby’s sex | Male | 7101 (51.3) | 542,231 (51.3) | 10,439 (51.7) | 1,954,758 (51.3) |
| Female | 6747 (48.7) | 514,663 (48.7) | 9757 (48.3) | 1,858,113 (48.7) | |
| Parity | 1st | 6058 (43.7) | 431,021 (40.8) | 8236 (40.8) | 1,527,460 (40.1) |
| 2nd | 4908 (35.4) | 337,616 (31.9) | 7388 (36.6) | 1,225,554 (32.1) | |
| 3rd | 1981 (14.3) | 170,827 (16.2) | 3131 (15.5) | 624,840 (16.4) | |
| 4+ | 901 (6.5) | 117,437 (11.1) | 1441 (7.1) | 435,042 (11.4) | |
| Prenatal care | No | 23 (0.2) | 3873 (0.4) | 32 (0.2) | 19,744 (0.5) |
| Yes | 13,825 (99.8) | 1,053,028 (99.6) | 20,164 (99.8) | 3,793,152 (99.5) | |
| Season of birth | Fall | 3553 (25.7) | 273,320 (25.9) | 5192 (25.7) | 974,949 (25.6) |
| Winter | 3418 (24.7) | 252,749 (23.9) | 5077 (25.1) | 925,952 (24.3) | |
| Spring | 3649 (26.4) | 275,830 (26.1) | 5126 (25.4) | 999,264 (26.2) | |
| Summer | 3228 (23.3) | 255,002 (24.1) | 4801 (23.8) | 912,731 (23.9) | |
| Adverse birth outcomes | LBW | 868 (6.3) | 65,890 (6.2) | 1106 (5.5) | 229,020 (6.0) |
| TLBW | 320 (2.5) | 23,836 (2.5) | 351 (1.9) | 81,120 (2.3) | |
| Preterm | 1162 (8.4) | 92,253 (8.7) | 1466 (7.3) | 314,990 (8.3) |
*
0, no formal education; 1, eight grade or less; 2, 9th grade through 12th grade–no diploma; 3, high school graduate or GED completed; 4, some college credit–no degree; 5, associate degree; 6, bachelor’s degree; 7, master’s degree; 8, doctorate or professional degree.