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Table 1 Baseline characteristics

From: Prenatal parental tobacco smoking, gene specific DNA methylation, and newborns size: the Generation R study

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
  1. aValues are presented as median (90 % range) or as number (%)
  2. bMissings; age at intake (n = 0), body mass index at intake (n = 1), gender (n = 0) birth weight (n = 0), gestational age at birth (n = 0)
  3. cANOVA and chi-square tests are used to test differences between the different smoking categories