Background: Determinants of the duration of exclusive breastfeeding (EBF) differ in effect and magnitude across populations. The present study aimed to identify factors associated with discontinuation of EBF in a municipality in northeastern Brazil, including variables that have received little or no attention in previous literature. Methods: This cohort study involved 1,344 mother-child pairs selected from maternity hospitals in Feira de Santana, Bahia, Brazil. Subjects were followed up for 6 months through monthly home visits, and discontinuation of EBF was recorded. Possible determinants were tested using Cox's four-level hierarchical survival model, taking into consideration the temporal proximity of the predisposing factors to interruption of EBF. Median duration of EBF was estimated using Kaplan-Meier's survival curve. Results: Median duration of EBF was 89 days. Out of the 19 variables tested, 9 showed an association with EBF cessation; of these, two had never been evaluated in Brazilian studies, namely, mother partner's appreciation for breastfeeding (hazard ratio [HR] 0.62; 95% confidence interval [95% CI] 0.48-0.79) and limiting the number of nighttime feeds at the breast (HR 1.58; 95% CI 1.11-2.23). Another two variables that had been previously evaluated, but had never been described as determinants of discontinuation of EBF showed association: presence of cracked nipples (HR 2.54; 95% CI 2.06-3.13) and prenatal care provided by public services (HR 1.34; 95% CI 1.17-1.55). Other variables showing associations with the outcome were: guidance on breastfeeding received at the hospital (HR 0.80; 95% CI 0.68-0.92), birth in a Baby-Friendly Hospital (HR 0.85; 95% CI 0.73-0.99), less than or equal to 8 years of maternal schooling (HR 1.34, 95% CI 1.17-1.53), mother working outside the home (HR 1.73; 95% CI 1.53-1.95), and use of a pacifier (HR 1.40; 95% CI 1.14-1.71). Conclusions: The study confirmed that the factors associated with EBF duration are multiple, variable, and dependent on the population being evaluated. Characteristics that had never been previously evaluated or described, at least in Brazilian studies, behaved as determinants of EBF in the present study, and thus allow to expand the existing list of factors determining this practice.
