Nicotine and cotinine in maternal and neonatal hair as markers of gestational smoking

Objective: To determine the extent of fetal exposure to cigarette smoke, which cannot be clearly extrapolated from maternal reports, the authors measured concentrations of nicotine and cotinine in maternal and neonatal hair and corroborated these measures with maternal history and measures of pregnancy outcome. Design: Prospective study of 94 mother-infant pairs. Setting: Newborn nurseries of two hospitals in Toronto. Participants: 93 mothers, including active smokers, passive smokers and nonsmokers, and their newborns (including one set of twins). Interventions: Hair collected from mothers and neonates shortly after birth was analysed by radioimmunoassay. Main outcome measures: Maternal data on demographic variables, obstetric history, diseases, drugs taken and smoking; infant data on demographic variables and birth indicators (gestational age, method of delivery, weight, head circumference, length, presence of meconium, need for resuscitation, need for special care and congenital malformations); hair concentrations of nicotine and cotinine. Results: Neonates of active smokers had more adverse outcomes than other infants, including lower birth weight, smaller head circumference, shorter length and more perinatal complications. The difference was statistically significant. Amounts of cotinine extracted from mothers' and infants' hair showed significant differences among active smokers, passive smokers and nonsmokers. When other people in the household and the mother smoked, neonatal hair concentrations of nicotine and cotinine in the infants were threefold higher than those in the infants of mothers who were the only smokers in their households. Conclusions: Hair concentrations of nicotine and cotinine are a powerful biological marker of the extent of intrauterine exposure to tobacco smoke.