Self-reported exposure to second-hand smoke and positive urinary cotinine in pregnant nonsmokers

Purpose: This cross-sectional study aimed to examine the association between self-reported exposure status to second-hand smoke and urinary cotinine level in pregnant nonsmokers.

Materials and methods: We recruited pregnant nonsmokers from the prenatal care clinics of a university hospital and two community health centers, and their urinary cotinine concentrations were measured.

Results: Among a total of 412 pregnant nonsmokers, the proportions of self-reported exposure to second-hand smoke and positive urinary cotinine level were 60.4% and 3.4%, respectively. Among those, 4.8% of the participants who reported exposure to second-hand smoke had cotinine levels of 40 ng/mL (the kappa value = 0.029, p = 0.049). Among those who reported living with smokers (n = 170), "smoking currently permitted in the whole house" (vs. not permitted at home) was associated with positive urinary cotinine in the univariable analysis. Furthermore, this variable showed a significant association with positive urinary cotinine in the stepwise multiple logistic regression analysis [Odds ratio (OR), 15.6; 95% Confidence interval (CI) = 2.1-115.4].

Conclusion: In the current study, the association between self-reported exposure status to second-hand smoke and positive urinary cotinine in pregnant nonsmokers was poor. "Smoking currently permitted in the whole house" was a significant factor of positive urinary cotinine in pregnant nonsmokers. Furthermore, we suggest that a complete smoking ban at home should be considered to avoid potential adverse effects on pregnancy outcomes due to second-hand smoke.