Influence of Maternal Environmental Tobacco Smoke Exposure Assessed by Hair Nicotine Levels on Birth Weight

Background: While the perinatal outcomes of active maternal smoking are well documented, results of theeffects of environmental tobacco smoke (ETS) exposure during pregnancy are inconsistent. We aimed to examinethe effect of ETS exposure, assessed by maternal hair nicotine levels at 35th week of gestation, on birth weightand the risk of small for gestational age (SGA) and low birth weight (LBW). Materials and
Methods: A totalof 871 non-smoking healthy pregnant women were recruited by one Korean hospital between 1 October 2006and 31 July 2007. Hair samples were collected and anthropometric questionnaires administered at 35th week ofgestation. The primary outcome was birth weight and secondary outcomes were the risk of babies being SGAand LBW.
Results: Log-transformed hair nicotine concentrations were inversely related with birth weight afteradjusting for confounding variables (β=-0.077, p=0.037). After stratifying hair nicotine levels by tertiles (T1,low [0.0-0.28 ng/mg]; T2, medium [0.29-0.62 ng/mg]; and T3, high [0.63-5.99 ng/mg]), the mean birth weightin each groups were 3,342g (T1) 3,296g (T2) and 3,290 g (T3), respectively. However the difference betweengroups was not statistically significant by analysis of co-variance (ANCOVA) adjusting for covariates (p=0.062).In logistic regression analysis, the risk of SGA was higher in the T3 (OR=1.59, 95%CI 1.05-2.42) than in thereference group (T1), after controlling for confounding variables. The risk of low birth weight (<2,500g, LBW)was not significantly higher (OR=1.44, 95%CI 0.95-2.19), but the risk of babies being below 3,000g birth weightwas increased in the T3 group (OR=1.53, 95%CI 1.00-2.36) compared with that in the T1 group.
Conclusions:Maternal ETS exposure during pregnancy was inversely related with birth weight. The risk of SGA increasedin the highest ETS exposure group compared with in the low exposure group. To prevent ETS exposure duringpregnancy, more comprehensive tobacco control policies are needed.