The Effects of Second-hand Smoke Exposure on Breast Milk Cotinine and Infant Urinary Cotinine

Background & Aims: Exposure to cigarette smoke affects the health of mothers and infants. The aim of this study was to examine the effects of second-hand smoke exposure on breast milk and infant urinary cotinine during breastfeeding. Methods: This cohort study was conducted on 45 breastfeeding mothers and infants exposed to second-hand cigarette smoke (exposed group), and 40 breastfeeding mothers and their infants not exposed to second-hand cigarette smoke (non-exposed group). The participants were chosen from mothers and infants who referred to one of the health centers affiliated with Tehran University of Medical Sciences, Tehran, Iran. Mothers’ breast milk and infant urine samples were collected twice at baseline (5–7 days after delivery) and 4 months after delivery. The cotinine levels in milk and urine were measured. Maternal nutritional status was assessed by 24-hour recall. All data were analyzed in SPSS. Results: There was a significant difference between the two groups regarding average level of cotinine in mothers’ breast milk, and urine of infants at baseline. This difference was also significant at 4 months postpartum (P < 0.001). Conclusion: The results showed that exposure to second-hand cigarette smoke during breastfeeding increases the cotinine level of mother's milk and infant urine at 4 months postpartum.