Brief cognitive behavioral therapy in pregnant women at risk of postpartum depression: Pre-post therapy study in a city in southern Brazil

•Brief CBT in pregnancy was effective in preventing PPD.•CBT improved interpersonal relationships and understanding of social status (OQ-45).•Education, among the risk factors for PPD, was decisive in the effectiveness of CBT. Postpartum depression (PPD) affects a high number of women, often the first manifestation of a mood disorder that will occur later in life, bringing serious consequences for the patient and her offspring. Depression today is the leading cause of disability worldwide. The aim of this study was to evaluate the effectiveness of a preventive cognitive behavioral therapy (CBT) for PPD. Pre-post therapy study, as part of a population-based cohort study. Pregnant women without a diagnosis of depression participated, who were divided into two groups: risk of depression (CBT) and a control group (without therapy). The preventive therapy consisted of six sessions of CBT, administered weekly. The Outcome Questionnaire (OQ-45) was used in all sessions. The Mini International Neuropsychiatric Interview and Beck Depression Inventory-II were used on three occasions. The final statistical analyses were performed by Poisson regression. The prevalence of PPD in the risk group was 5.5% and in the control group 2.2%, with no difference between the groups (PR 1.66 95% CI 0.44-6.18). The OQ-45 averages gradually reduced during the therapy sessions, indicating therapeutic progress. Schooling was an associated factor, both with the manifestation of PPD and with the greater effectiveness of the therapy. Rate of 40.5% refusal to preventive treatment and absence of a group with similar characteristics in another therapy model. Brief cognitive behavioral therapy applied by mental health professionals with basic training was effective in preventing the manifestation of PPD.