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Table 3 Associations between maternal BaP-DNA adducts and risk of PB, and between dietary vitamins, folate, carotene intake and risk of PB by different pregnancy windows

From: Effects of Benzo[a]pyrene-DNA adducts, dietary vitamins, folate, and carotene intakes on preterm birth: a nested case–control study from the birth cohort in China

Characteristics & time windows ORa 95%CI ORb 95%CI
Maternal BaP-DNA adducts (µg/gDNA)
 Per interquartile increase 1.27 0.95, 1.67 1.28 0.95, 1.72
  > 3.21 compared to ≤ 3.21 2.05 1.05, 4.01 2.09 1.06, 4.11
Dietary intake > mean levels compared to ≤ mean levels
 Vitamin C (mg)
  Preconception & during pregnancy 0.43 0.21, 0.87 0.39 0.19, 0.80
  During pregnancy only 0.55 0.27, 1.10 0.48 0.24, 0.99
  Preconception only 0.39 0.18, 0.84 0.34 0.16, 0.76
 Vitamin A (µg RE)
  Preconception & during pregnancy 0.47 0.23, 0.96 0.43 0.21, 0.89
  During pregnancy only 0.56 0.28, 1.14 0.52 0.25, 1.07
  Preconception only 0.39 0.19, 0.81 0.34 0.16, 0.71
 Vitamin E (mg)
  Preconception & during pregnancy 0.49 0.23, 1.04 0.45 0.21, 0.97
  During pregnancy only 0.57 0.27, 1.19 0.54 0.26, 1.13
  Preconception only 0.38 0.19, 0.80 0.35 0.16, 0.73
 Folate (µg)
  Preconception & during pregnancy 0.32 0.16, 0.67 0.30 0.14, 0.63
  During pregnancy only 0.40 0.20, 0.81 0.38 0.19, 0.78
  Preconception only 0.38 0.18, 0.79 0.35 0.16, 0.74
 Carotene (µg)
  Preconception & during pregnancy 0.43 0.21, 0.89 0.37 0.17, 0.78
  During pregnancy only 0.50 0.24, 1.01 0.43 0.21, 0.90
  Preconception only 0.39 0.19, 0.81 0.33 0.16, 0.71
  1. aAdjusted for maternal age, education, family income per month, maternal BMI, passive smoking, parity, C-section, newborn gender, activity, and employment during pregnancy
  2. bAdditional adjusted for supplementation status (ever, never)
  3. Abbreviations: PB Preterm birth, BaP Benzo[a]Pyrene, OR Odds Ratio, CI Confidence interval