Objective. Most biomarker studies of maternal smoking have been based on a single blood or urinary cotinine value, which is inadequate in capturing maternal tobacco exposure over the entire pregnancy. This thesis used maternal hair biomarkers to investigate the association between maternal active and passive smoking, and birthweight for gestational age (BW for GA). / Methods. Subjects were 444 term controls drawn from 5,337 participants of a multi-centre nested case-control study of preterm birth in Montreal. Maternal hair, collected after delivery, was measured for average nicotine and cotinine concentration across the pregnancy, assuming hair growth of 1 cm/month. The BW for GA z-score used Canadian population-based standards. Multiple linear regression was used to assess effects on the z-score, after controlling for potential confounders. / Results. In regression models for maternal active smoking analysis, the addition of hair nicotine to models containing either self-report or hair cotinine or both self-report and cotinine explained significantly more variance in the BW for GA z-score (p=0.009, p=0.017, and p=0.033, respectively). In maternal passive smoking analysis, no significant effect of ETS on BW for GA was found using hair biomarkers. / Conclusion. These results indicate that hair biomarkers are sensitive tools capable of predicting reductions in birthweight for maternal active smoking. The stronger results obtained for nicotine are reflective of the fact that hair nicotine is a better measure of maternal smoking, but it could also suggest that nicotine plays an aetiologic role in affecting foetal growth.

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