Table 1 Study population characteristics according to maternal cotinine levels
All | Maternal cotinine (ng/ml) | P value | |||
|---|---|---|---|---|---|
Non-smokers | Passive smokers | Active smokers | |||
(n = 1150) | (n = 612) | (n = 429) | (n = 109) | ||
Mothers | |||||
Age (years) | 31.3 ± 4.4 | 31.9 ± 4.2 | 30.5 ± 4.5 | 31.2 ± 4.6 | < 0.001 |
BMI (kg/m2) | 21.1 ± 3.1 | 21.2 ± 3.2 | 20.9 ± 2.8 | 21.5 ± 4.0 | 0.167 |
Parity | < 0.001 | ||||
Primiparous | 495 (43.0) | 236 (38.6) | 223 (52.0) | 36 (33.0) | |
Multiparous | 652 (56.7) | 373 (60.9) | 206 (48.0) | 73 (67.0) | |
Missing data | 3 (0.3) | 3 (0.5) | 0 (0.0) | 0 (0.0) | |
Alcohol intake during pregnancy | 0.061 | ||||
No | 1016 (88.3) | 551 (90.0) | 375 (87.4) | 90 (82.6) | |
Yes | 134 (11.7) | 61 (10.0) | 54 (12.6) | 19 (17.4) | |
Education (years) | < 0.001 | ||||
≤ 12 | 468 (40.7) | 216 (35.3) | 182 (42.4) | 70 (64.2) | |
> 12 | 681 (59.2) | 395 (64.5) | 247 (57.6) | 39 (35.8) | |
Missing data | 1 (0.1) | 1 (0.2) | 0 (0.0) | 0 (0.0) | |
Annual household income (million JPY) | 0.002 | ||||
5 < | 743 (64.6) | 368 (60.1) | 295 (68.8) | 80 (73.4) | |
≥ 5 | 407 (35.4) | 244 (39.9) | 134 (31.2) | 29 (26.6) | |
Infants | |||||
Sex | 0.095 | ||||
Male | 579 (50.3) | 290 (47.4) | 232 (54.1) | 57 (52.3) | |
Female | 571 (49.7) | 322 (52.7) | 197 (45.9) | 52 (47.7) | |
Birth weight (g) | 3070.2 ± 366.6 | 3065.0 ± 358.3 | 3118.2 ± 353.9 | 2910.7 ± 415.5 | < 0.001 |
Gestational age (weeks) | 0.338 | ||||
Preterm (< 37 weeks) | 28 (2.4) | 17 (2.8) | 7 (1.6) | 4 (3.7) | |
Full-term (≥ 37 weeks) | 1122 (97.6) | 595 (97.2) | 422 (98.4) | 105 (96.3) | |
ADHD symptoms | 0.011 | ||||
No | 962 (83.7) | 527 (86.1) | 353 (82.3) | 82 (75.2) | |
Yes | 188 (16.3) | 85 (13.9) | 76 (17.7) | 27 (24.8) | |