postpartum thyroiditis (ppt) is an autoimmune thyroid dysfunction that occurs in the first year after delivery. we evaluated the prevalence and clinical evolution of ppt in 115 pregnant women between the 16th and 20th weeks of gestation. we studied both thyroid function (t3, t4, t4l, tsh) and the presence of antithyroid antibodies (antithyroglobulin and antiperoxidase). reevaluation was done six months postpartum. in the first phase, 12 (10.4%) were tpo-ab positive: two (16.6%) had a miscarriage between the 5th and 6th month, three (25%) were euthyroid, three (25%) subclinic hypothyroidism and four (33,3%) ppt. the most frequent symptom was fatigue (4/4). all women showed risk factors for ppt. based on our data, we recommend that pregnant women with risk factor for ppt should be screened during pregnancy and the postpartum period for the development of thyroid dysfunction.