The aim of the study was to investigate the characteristics of infant development at four, eight and twelve months of age, as result of postpartum depression. The prevalence of Postpartum Depression - measured by the Edinburgh Postnatal Depression Scale - at four months after delivery was 30.3%; at eight months, 26.4%; and at 12 months, 25.0%. Chi-square tests were used to compare children of mothers with and without Postpartum Depression in relation to developmental milestones. It was found developmental delay in infants of mothers with Postpartum Depression in: two interactional indicators at four months, two motor indicators at eight months and one gross motor indicator at twelve months. However, children of mothers with Postpartum Depression showed better results in one fine motor and in two language items at 12 months. The results point to the necessity of considering external and internal factors of mother and infant in the study of the effects of maternal depression on child development.