RESUMO
Preterm birth (PTB) and postpartum depression (PPD) are important public health issues, and although literature mainly supports the association between them, some reviews have highlighted methodological limitations in the studies in this field, restricting the interpretation of such finding. This study aimed at assessing the association between PTB and PPD, by comparing groups of preterm and full-term mothers in two Brazilian cities with contrasting sociodemographic indicators. This prospective convenience cohort study assessed 1421 women during pregnancy, at childbirth, and in the postpartum period. The Edinburgh Postnatal Depression Scale (EPDS) was administrated to assess PPD within 6 months after delivery and women were considered probably depressed if scores were EDPS ≥ 12. PTB was defined as the delivery before 37 completed weeks of pregnancy. A multivariate Poisson regression was used to estimate relative risk for PPD in mothers of preterm infants, and the final analysis models were adjusted for psychosocial variables, selected according to the directed acyclic graph (DAG) approach. Frequencies of PPD were not significantly different in mothers of preterm and full-term infants, in neither city. In the final adjusted model, PTB was not associated with PPD. The association between PTB and PPD was not confirmed in two large samples from two Brazilian cities with contrasting socioeconomic profile. However, maternal health during pregnancy plays an important role in predicting PPD. Prenatal care should promote maternal mental health as an effort towards decreasing unfavored outcomes for mothers, infants, and families.