RESUMO
OBJECTIVES: This study was performed to examine the relationship between maternal exposure to environmental tobacco smoke (ETS) and pregnancy outcomes (low birth weight or preterm baby) in a prospective cohort study. METHODS: We made a pregnant women's cohort, and followed the pregnancy outcomes, between May 1st 2001 and August 31st 2002. We surveyed 2, 250 women who visited our hospital during their 35th gestational week, with a self-administered questionnaire. The final total of mother-infant pairs analyzed in this study was 1, 712. We used a multiple logistic regression analysis to analyze the effect of maternal ETS on the incidence of preterm or low birth weight, and a linear regression analysis for the birth weight and gestational age. RESULTS: Higher exposure to ETS (> or =1 hours/day) during pregnancy was more negatively associated with the gestational age and birth weight, than no exposure to ETS (no or less than 1hour). Maternal exposure to ETS was associated with preterm baby (adjusted odds ratio (AOR) 1.7; 95% confidence interval (CI) 0.9, 3.3) and low birth weight (AOR 2.3; 95% CI 0.9, 5.5). In addition, we found that maternal ETS may reduce the birth weight by 70g after adjusting for potential confounding factors. CONCLUSIONS: This study suggests that maternal exposure to ETS during pregnancy may increase the frequency of low birth weights and preterm births.