Table 1 Characteristics of the study population according to maternal cotinine levels
Maternal cotinine (ng/ml) | All (n = 3216) | ≦ 0.21 (n = 1882) | 0.22-0.51 (n = 531) | 0.52–11.48 (n = 535) | 11.49 ≦ (n = 268) | p value | |
|---|---|---|---|---|---|---|---|
Parent | |||||||
Maternal age (years) | 31.3 ± 4.7 | 32.0 ± 4.6 | 30.1 ± 4.4 | 30.1 ± 5.0 | 30.7 ± 4.9 | < 0.001 | |
Paternal age (years) | 32.9 ± 5.6 | 33.4 ± 5.4 | 31.9 ± 5.2 | 32.2 ± 5.9 | 33.0 ± 5.9 | < 0.001 | |
Maternal BMI (kg/m2) | 21.1 ± 3.2 | 21.2 ± 3.2 | 20.8 ± 2.9 | 21.0 ± 2.9 | 21.3 ± 3.6 | 0.083 | |
Parity | 0 | 1051 (32.7) | 549 (29.2) | 217 (40.9) | 221 (39.4) | 64 (23.9) | < 0.001 |
≧ 1 | 1732 (53.9) | 1086 (57.7) | 240 (45.2) | 241 (45.0) | 165 (61.6) | ||
Alcohol intake during pregnancy | Yes | 316 (9.8) | 157 (4.9) | 60 (11.3) | 64 (12.0) | 35 (13.1) | 0.015 |
Maternal smoking at first trimester | Yes | 185 (5.8) | 9 (0.5) | 4 (0.7) | 14 (2.6) | 158 (59.0) | < 0.001 |
Maternal education (years) | ≦ 12 | 1051 (32.7) | 655 (34.8) | 219 (41.2) | 266 (49.7) | 177 (66.0) | < 0.001 |
≧ 13 | 1732 (53.6) | 1198 (63.7) | 302 (56.9) | 262 (49.0) | 85 (31.7) | ||
Paternal education (years) | ≦ 12 | 1362 (42.4) | 687 (36.5) | 227 (42.7) | 280 (52.3) | 168 (62.7) | 0.001 |
≧ 13 | 1784 (55.5) | 1155 (61.4) | 289 (54.4) | 248 (46.4) | 92 (34.3) | ||
Paternal smoking at first trimester | Yes | 1620 (50.4%) | 697 (37.5) | 330 (62.7) | 371 (70.4) | 222 (83.5) | < 0.001 |
Family income during pregnancy (million JPY) | 5> | 1837 (57.1) | 1015 (53.9) | 312 (58.8) | 328 (61.3) | 182 (67.9) | < 0.001 |
≧ 5 | 985 (30.6) | 651 (34.6) | 151 (28.4) | 126 (23.6) | 57 (21.3) | ||
Family income at SDQ completed (million JPY) | 5> | 1562 (48.6) | 833 (44.3) | 273 (51.4) | 292 (54.6) | 164 (61.2) | < 0.001 |
≧ 5 | 1479 (46.0) | 950 (50.5) | 234 (44.1) | 208 (38.9) | 87 (32.5) | ||
Marital status | Married | 3007 (93.5) | 1790 (95.1) | 497 (93.6) | 481 (89.9) | 239 (89.2) | < 0.001 |
Child | |||||||
Sex | Boy | 1621 (50.4) | 929 (49.4) | 276 (52.0) | 269 (50.3) | 147 (54.9) | 0.380 |
Girl | 1595 (49.6) | 953 (50.6) | 255 (48.0) | 266 (49.7) | 121 (45.1) | ||
Birth weight (g) | 3048 ± 385 | 3060 ± 375 | 3041 ± 405 | 3060 ± 391 | 2960 ± 393 | 0.001 | |
Birth length (cm) | 49.0 ± 2.0 | 49.1 ± 1.9 | 49.1 ± 2.1 | 49.0 ± 2.0 | 48.7 ± 2.0 | 0.024 |