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Table 4 Adjusted association between serum and meconium biomarkers of tobacco smoke exposure and infant birth weight.*

From: A prospective cohort study of biomarkers of prenatal tobacco smoke exposure: the correlation between serum and meconium and their association with infant birth weight

  N Mean Birth Weight Change in Birth Weight
(95% CI)
Confidence Limit Difference†
Meconium NIC     
   Unexposed (< LOD) 62 3386 Ref ---
   SHS (LOD - 10 ng/g) 212 3251 -136 (-295, 24) 320
   Active (> 10 ng/g) 28 3252 -135 (-395, 126) 520
   Continuous† 302 --- -62 (-178, 53) 231
Meconium COT     
   Unexposed (< LOD) 97 3317 Ref ---
   SHS (LOD - 5 ng/g) 171 3286 -27 (-175, 120) 295
   Active (> 5 ng/g) 34 3207 -106 (-348, 135) 482
   Continuous† 302 --- -61 (-132, 10) 143
Meconium 3HC     
   Unexposed (< LOD) 135 3335 Ref ---
   SHS (LOD - 10 ng/g) 139 3235 -100 (-246, 46) 292
   Active (> 10 ng/g) 28 3278 -57 (-307, 192) 500
   Continuous† 302 --- -30 (-96, 36) 132
Mean Serum COT     
   Unexposed (< LOD) 122 3377 Reference ---
   SHS (LOD to 3 ng/mL) 148 3265 -112 (-264, 41) 305
   Active (> 3 ng/mL) 32 3188 -189 (-462, 84) 545
   Continuous† 302 --- -60 (-135, 16) 150
16 Week Serum COT     
   Unexposed (< LOD) 101 3312 Reference ---
   SHS (LOD to 3 ng/mL) 162 3292 -20 (-173, 132) 305
   Active (> 3 ng/mL) 32 3203 -109 (-386, 168) 554
   Continuous† 295 --- -59 (-125, 7) 132
26 Week Serum COT     
   Unexposed (< LOD) 126 3282 Reference ---
   SHS (LOD to 3 ng/mL) 138 3302 20 (-135, 175) 305
   Active (> 3 ng/mL) 29 3144 -138 (-425, 150) 554
   Continuous† 293 --- -41 (-104, 21) 125
Birth Serum COT     
   Unexposed (< LOD) 121 3416 Reference ---
   SHS (LOD to 3 ng/mL) 131 3319 -97 (-248, 54) 302
   Active (> 3 ng/mL) 29 3226 -190 (-462, 82) 545
   Continuous† 281 --- -40 (-104, 24) 128
  1. *-Adjusted for maternal age (18 to <25, 25 to <35, and 35+ years), race (non-Hispanic white, non-Hispanic black, and other), education (< 12, 12, and >12 years), martial status (married and unmarried), depression (minimal, mild, and moderate/severe), parity (0, 1, and >1) and maternal weight.
  2. †-Calculated by subtracting the lower 95% confidence limit from the upper 95% confidence limit
  3. ‡-Coefficients represent change in birth weight for a 10-fold increase in metabolite concentration.