Table 1 Individual characteristics and PM air pollution concentrations of 824,011 singleton term births across three birth status by mothers’ employment status, Seoul, Korea, 2002–2012
|  | Employed mothers (n = 279,856) | Non-employed mothers (n = 544,155) | ||||
|---|---|---|---|---|---|---|
Normal | SGA excluding LBW | LBW | Normal | SGA excluding LBW | LBW | |
(n = 244,414; 87.3%) | (n = 31,294; 11.2%) | (n = 4,148; 1.5%) | (n = 474,765, 87.2%) | (n = 60,774, 11.2%) | (n = 8,616; 1.6%) | |
Birthweight (kg) | 3.37 ± 0.33 | 2.77 ± 0.13 | 2.31 ± 0.16 | 3.38 ± 0.34 | 2.76 ± 0.13 | 2.31 ± 0.17 |
Female sex, n (%) | 114,624 (46.9) | 19,313 (61.7) | 2,461 (59.3) | 211,911 (46.7) | 37,086 (61.0) | 5,186 (60.2) |
Gestational age (weeks) | 39.22 ± 1.07 | 39.29 ± 0.97 | 38.21 ± 1.06 | 39.19 ± 1.08 | 39.28 ± 0.97 | 38.27 ± 1.09 |
Maternal age (years) | 31.01 ± 3.30 | 30.84 ± 3.27 | 31.18 ± 3.50 | 30.66 ± 3.86 | 30.39 ± 3.93 | 30.85 ± 4.20 |
20–24 | 3,666 (1.5) | 442 (1.4) | 69 (1.7) | 24,821 (5.2) | 3,882 (6.4) | 568 (6.6) |
25–29 | 79,446 (32.5) | 10,855 (34.7) | 1,325 (31.9) | 159,036 (33.5) | 21,417 (35.2) | 2,667 (31) |
30–34 | 126,570 (51.8) | 15,911 (50.8) | 2,090 (50.3) | 217,912 (45.9) | 26,808 (44.1) | 3,786 (43.9) |
35–39 | 31,667 (13.0) | 3,720 (11.9) | 574 (13.8) | 65,075 (13.7) | 7,671 (12.6) | 1,377 (16) |
≥ 40 | 3,065 (1.3) | 366 (1.2) | 90 (2.2) | 7,921 (1.7) | 996 (1.6) | 218 (2.5) |
Nulliparity | 161,663 (66.1) | 23,621 (75.5) | 3,143 (75.8) | 241,127 (50.8) | 37,269 (61.3) | 5,363 (62.2) |
Maternal education level (years) | ||||||
 <  7 | 154 (0.1) | 17 (0.1) | 5 (0.1) | 1,463 (0.3) | 257 (0.4) | 52 (0.6) |
 7–12 | 34,570 (14.1) | 4,318 (13.8) | 697 (16.8) | 180,995 (38.1) | 23,271 (38.3) | 3,635 (42.2) |
 >  12 | 209,690 (85.8) | 26,959 (86.1) | 3446 (83.1) | 292,307 (61.6) | 37,246 (61.3) | 4,929 (57.2) |
Birth season | ||||||
 Spring | 59,540 (24.4) | 7,672 (24.5) | 981 (23.6) | 118,082 (24.9) | 15,292 (25.2) | 2,176 (25.3) |
 Summer | 58,753 (24.0) | 7,363(23.5) | 992 (23.9) | 112,865 (23.8) | 14,306 (23.5) | 2,111 (24.5) |
 Fall | 64,437 (26.4) | 8,408 (26.9) | 1,147 (27.7) | 120,076 (25.3) | 15,843 (26.1) | 2,230 (25.9) |
 Winter | 61,684 (25.2) | 7,851 (25.1) | 1,028 (24.8) | 123,742 (26.1) | 15,333 (25.2) | 2,099 (24.4) |
PM10 during pregnancy [μg/m3] | ||||||
 1 year before birth | 56.24 ± 9.42 | 56.22 ± 9.45 | 55.90 ± 9.24 | 58.75 ± 10.08 | 58.8 ± 10.17 | 58.28 ± 10.20 |
 Entire pregnancy | 55.68 ± 10.21 | 55.65 ± 10.24 | 55.32 ± 10.16 | 58.14 ± 10.84 | 58.20 ± 10.91 | 57.74 ± 11.00 |
 First trimester | 56.75 ± 15.63 | 56.83 ± 15.68 | 56.52 ± 15.30 | 59.06 ± 16.73 | 59.13 ± 16.87 | 58.42 ± 16.49 |
 Second trimester | 55.52 ± 15.47 | 55.53 ± 15.57 | 55.10 ± 15.19 | 57.85 ± 16.42 | 58.00 ± 16.50 | 57.69 ± 16.18 |
 Third trimester | 54.85 ± 17.24 | 54.69 ± 17.30 | 54.15 ± 17.27 | 57.58 ± 18.09 | 57.52 ± 18.17 | 57.10 ± 18.03 |
PM2.5 during pregnancy [μg/m3] a | ||||||
 1 year before birth | 28.35 ± 6.21 | 28.30 ± 6.25 | 28.17 ± 5.96 | 29.60 ± 7.00 | 29.65 ± 7.08 | 29.44 ± 7.03 |
 Entire pregnancy | 28.10 ± 6.55 | 28.03 ± 6.59 | 27.94 ± 6.29 | 29.32 ± 7.33 | 29.33 ± 7.39 | 29.22 ± 7.40 |
 First trimester | 28.60 ± 8.12 | 28.59 ± 8.18 | 28.40 ± 7.77 | 29.78 ± 9.04 | 29.82 ± 9.14 | 29.61 ± 9.03 |
 Second trimester | 28.08 ± 7.95 | 28.04 ± 7.98 | 28.84 ± 7.68 | 29.23 ± 8.81 | 29.29 ± 8.86 | 29.22 ± 8.82 |
 Third trimester | 27.70 ± 8.51 | 27.58 ± 8.51 | 27.39 ± 8.48 | 28.97 ± 9.31 | 28.94 ± 9.38 | 28.83 ± 9.35 |