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Table 1 Characteristics of mother-newborn pairs according to self-reported tobacco smoke exposure during pregnancy

From: Placental mitochondrial DNA and CYP1A1 gene methylation as molecular signatures for tobacco smoke exposure in pregnant women and the relevance for birth weight

Variable All (n = 382) Non-smokers (n = 255) Past-smokers (n = 65) Smokers (n = 62) p value*
Newborn
 Sex      0.47
  Male 188 (49.2%) 120 (47.1%) 34 (52.3%) 34 (54.8%)  
  Female 194 (50.8%) 135 (52.9%) 31 (47.7%) 28 (45.2%)  
 Ethnicity      0.73
  European-Caucasian 332 (86.9%) 223 (87.4%) 57 (87.7%) 52 (83.9%)  
  Non-European 50 (13.1%) 32 (12.6%) 8 (12.3%) 10 (16.1%)  
 Gestational age, w 39.2 ± 1.2 39.3 ± 1.2 39.2 ± 1.3 39.2 ± 1.2 0.82
 Birth weight, g 3429 ± 426 3472 ± 424 3437 ± 423 3247 ± 395 0.0009
 Birth length, cm 50.3 ± 1.9 50.5 ± 2.0 50.5 ± 1.7 49.5 ± 1.8 0.0007
Mother
 Age, year 29.0 ± 4.7 29.4 ± 4.5 28.9 ± 4.9 27.7 ± 4.8 0.03
 Pre-pregnancy BMI, kg/m2 24.3 ± 4.5 24.2 ± 4.4 24.8 ± 5.3 24.2 ± 4.1 0.65
 Maternal education      <0.0001
  Low 51 (13.3%) 26 (10.2%) 6 (9.2%) 19 (30.6%)  
  Middle 131 (34.3%) 77 (30.2%) 25 (38.5%) 29 (46.8%)  
  High 200 (52.4%) 152 (59.6%) 34 (52.3%) 14 (22.6%)  
 Medication usea      0.57
  None 134 (37.8%) 92 (39.5%) 21 (32.3%) 21 (37.5%)  
 Alcohol consumption      0.03
  Occasionally 73 (19.1%) 42 (16.5%) 20 (30.8%) 11 (17.7%)  
 Physical activity (>20 min)b      0.40
  <1 times per week 122 (33.3%) 82 (33.3%) 19 (29.7%) 21 (36.8%)  
  1 times per week 86 (23.4%) 63 (25.6%) 15 (23.4%) 8 (14.0%)  
  >2 times per week 159 (43.3%) 101 (41.1%) 30 (46.9%) 28 (49.2%)  
 Parity      0.42
  1 200 (52.3%) 132 (51.8%) 36 (55.4%) 32 (51.6%)  
  2 142 (37.2%) 91 (35.7%) 25 (38.5%) 26 (41.9%)  
  ≥3 40 (10.5%) 32 (12.5%) 4 (6.1%) 4 (6.5%)  
 Cigarettes before pregnancy 11.0 ± 6.9 10.3 ± 6.7  
 Cigarettes during pregnancy 7.8 ± 4.6  
  1. Data are presented as arithmetic mean ± standard deviation (SD) or number (%)
  2. * p value derived from one-way ANOVA or Chi square tests in case of continuous or categorical variables respectively
  3. aMedication use: occasional use of paracetamol or antibiotics (28 missing data)
  4. bMissing data for 15 subjects