RESUMO
AIMS: Our objective was to evaluate the level of pregnant women's exposure to tobacco smoke by urinary cotinine testing at prenatal examinations, and to examine the effects of disclosing the results of urinary cotinine tests to pregnant women and their families on their smoking activities. METHODS: A prospective cohort study was conducted, enrolling 420 pregnant women who attended prenatal examinations at five private clinics in Japan. Urinary cotinine testing and a questionnaire survey regarding smoking status were conducted in early, middle, and late pregnancy. Urinary cotinine values were measured semiquantitatively using NicCheck I test strips. The results of each urinary cotinine test were handed to the pregnant woman and shared with her family. RESULTS: The percentages of urinary cotinine-positive subjects in middle and late pregnancy were significantly decreased compared with early pregnancy (P<0.001 each). Among the active smokers, there were no significant differences in the urinary cotinine-positive rates and the numbers of cigarettes among the three stages. In contrast, the urinary cotinine-positive rates in the passive smokers in late pregnancy were significantly lower than in early pregnancy (P=0.045) and those in non-smokers in middle and late pregnancy were also lower than in early pregnancy (P=0.001, P<0.001). The numbers of cigarettes smoked by persons close to the passive smokers in middle and late pregnancy were significantly lower than in early pregnancy (P<0.001). CONCLUSIONS: The feedback of the urinary cotinine test results at prenatal examinations decreased the level of exposure of pregnant passive smokers and non-smokers to tobacco smoke.