Effect of Passive Smoking Using Maternal and Neonatal Salivary Cotinine Measurements

Background: In Japan, the rate of passive smoking among pregnant women is 52.7%, and smokers are usually their husbands (80.8%). Fetal environmental tobacco smoke has been measured using cotinine levels in maternal and neonatal hair, urine, or umbilical cord blood. However, using saliva from neonates immediately after birth has not been explored among noninvasive methods. Objective: The aims of this study were to (a) determine the relationship between fathers' smoking status during pregnancy and neonatal and maternal salivary cotinine immediately after delivery and (b) evaluate the potential use of salivary cotinine measurements immediately after birth to determine the exposure of the neonates to passive smoke. Method: A cross-sectional survey design was used. The participants were 34 pairs of nonsmoking mothers and their neonates who had visited for a health check-up at a general hospital in Tokyo. Saliva samples were collected from mothers and their neonates within 24 hours of delivery. All samples were analyzed using an enzyme-linked immunosorbent assay. Information about maternal age, neonate's birth weight, and smoking status of the father were obtained by interview and questionnaire. Results: Salivary cotinine levels in neonates and mothers with indoor-smoking fathers were significantly higher compared with those in neonates and mothers with nonsmoking and outdoor-smoking fathers. A very strong positive correlation was observed between neonatal and maternal cotinine levels. Conclusion: Smoking indoors by the father affected the mother and neonate. Salivary cotinine measurement is a feasible method to evaluate passive exposure of neonates to tobacco smoke.