Hair Concentrations of Nicotine and Cotinine in Women and Their Newborn Infants

BACKGROUND: To date, no biological markers have been identified that can predict the extent of fetal exposure to the toxic constituents of cigarette smoke. A variety of xenobiotic agents have been shown to accumulate in growing hair. PATIENTS AND METHODS: We measured maternal and neonatal hair concentrations of nicotine and cotinine in 94 mother-infant pairs. Mothers who were active smokers, nonsmokers, and passive smokers and their infants were included. RESULTS: Mothers who were active smokers (n = 36) had mean (SEM) hair concentrations of 19.2 (4.9) ng/mg for nicotine and 6.3 (4.0) ng/mg for cotinine, significantly higher than concentrations in nonsmokers (n = 35) (1.2 0.4 ng/mg for nicotine and 0.3 0.06 ng/mg for cotinine, P < .0001). Infants of smokers had mean hair concentrations of 2.4 (0.9) ng/mg for nicotine (range, 0 to 27.3 ng/mg) and 2.8 (0.8) ng/mg for cotinine (range, 0 to 12.2 ng/mg), significantly higher than concentrations in infants of nonsmokers (0.4 0.09 ng/mg for nicotine and 0.26 0.04 ng/mg for cotinine, P < .01). Mothers with passive smoke exposure and their infants (n = 23) had significantly higher hair concentrations of nicotine (3.2 0.8 ng/mg for mothers and 0.28 0.05 ng/mg for infants) and cotinine (0.9 0.3 ng/mg for mothers and 0.6 0.15 ng/mg for infants) than nonsmoking mothers and their infants (P < .01). There was a significant correlation between maternal and neonatal hair concentrations of nicotine (r = .49, P < .001) or cotinine (r = .85, P = .0001). CONCLUSIONS: This is the first biochemical evidence that infants of passive smokers are at risk of measurable exposure to cigarette smoke. Hair accumulation of cigarette smoke constituents reflects long-term systemic exposure to these toxins and therefore may be well correlated with perinatal risks.