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Table 1 Baseline characteristics
| Characteristic | Prenatal maternal tobacco smoking | |||||
|---|---|---|---|---|---|---|
| No (n = 334) | First trimester only (n = 47) | Continued | ||||
| All (n = 125) | <5 cigarettes per day (n = 41) | ≥5 cigarettes per day (n = 56) | P valuec | |||
| Maternal | ||||||
| Age at intake (years)a, b | 31.5 (22.5–38.1) | 30.5 (20.1–38.3) | 28.5 (19.0–37.7) | 29.4 (20.0–37.5) | 28.4 (18.4–39.9) | <0.001 |
| Body mass index at intake (kg/m2)a, b | 23.1 (19.5–32.2) | 23.2 (19.6–33.1) | 23.7 (18.2–32.5) | 22.8 (18.2–33.6) | 24.8 (18.0–33.9) | NS |
| Education, n (%) | <0.001 | |||||
| Primary education | 6 (1.8) | 4 (8.5) | 12 (9.6) | 0 (0) | 10 (17.9) | |
| Secondary education | 134 (40.1) | 21 (44.7) | 78 (62.4) | 23 (56.1) | 34 (60.7) | |
| Higher education | 193 (57.8) | 22 (46.8) | 33 (26.4) | 17 (41.5) | 11 (19.6) | |
| Missing | 1 (0.3) | 0 (0.0) | 2 (1.6) | 1 (2.4) | 1 (1.8) | |
| Parity (%) | NS | |||||
| 0 | 220 (65.9) | 34 (72.3) | 82 (65.6) | 28 (68.3) | 35 (62.5) | |
| ≥1 | 114 (34.1) | 13 (27.7) | 43 (34.4) | 13 (31.7) | 21 (37.5) | |
| Folic acid supplement use during pregnancy, n (%) | <0.001 | |||||
| Start preconception | 188 (56.3) | 18 (38.3) | 29 (23.2) | 11 (26.8) | 15 (26.8) | |
| Start postconception | 84 (25.1) | 19 (40.4) | 36 (28.8) | 13 (31.7) | 13 (23.2) | |
| No | 25 (7.5) | 7 (14.9) | 33 (26.4) | 10 (24.4) | 14 (25) | |
| Missing | 37 (11.1) | 3 (6.4) | 27 (21.6) | 7 (17.1) | 14 (25) | |
| Paternal smoking, n (%) | 125 (37.4) | 28 (59.6) | 91 (72.8) | 14 (34.1) | 9 (16.1) | <0.001 |
| <5 cigarettes per day | 57 (17.1) | 9 (19.1) | 17 (13.6) | 7 (17.1) | 17 (30.4) | |
| ≥5 cigarettes per day | 67 (20.1) | 18 (38.3) | 73 (58.4) | 4 (9.8) | 39 (69.6) | |
| Newborns | ||||||
| Boys, n (%) | 195 (58.4) | 21 (44.7) | 81 (64.8) | 26 (63.4) | 34 (60.7) | NS |
| Birth weighta, b | 3500 (2536–4383) | 3410 (2154–4219) | 3195 (2348–4081) | 3175 (2663–4252) | 3210 (2334–4150) | <0.001 |
| Gestational age at birtha, b | 40.3 (37.6–42.0) | 40.3 (36.5–41.9) | 40.1 (37.1–42.5) | 40.6 (37.0–42.9) | 40.2 (36.9–42.3) | NS |
| IGF2DMR methylation (%)a | 54.0 (44.6–62.0) | 52.2 (44.5–61.1) | 51.6 (43.9–61.3) | 52.0 (44.0–61.2) | 51.1 (41.2–63.9) | 0.033 |
| H19 methylation (%)1 | 30.0 (25.5–34.0) | 30.8 (27.1–34.1) | 30.2 (23.7–34.8) | 29.8 (21.5–33.0) | 30.2 (23.1–37.0) | NS |
