Environmental tobacco smoke and breastfeeding duration.

The effect of smoking on breastfeeding duration was investigated in a population-based birth cohort study of 1,098 Brazilian infants. There were few losses to follow-up (3.2%) in the first 6 months. Maternal smoking was strongly associated with breastfeeding duration, even after adjustment for confounding. Compared with nonsmokers, mothers smoking 20 or more cigarettes daily presented an odds ratio of 1.94 for breastfeeding for less than 6 months. Environmental tobacco smoke was also an independent risk factor. After adjustment for maternal smoking and other confounders, households where more than 10 cigarettes were smoked daily by persons other than the mother presented an odds ratio of 1.48 compared with those without smokers. These results remained unchanged after stratification for maternal smoking. This is the first report of a possible effect of environmental tobacco smoke on breastfeeding duration.