OBJECTIVE To assess the incidence of post-partum thyropathies in women with positive antibodies against thyroid peroxidase in the second trimester of pregnancy. METHODS Based on a cross-sectional study of the prevalence of abnormal laboratory parameters of thyroid function in a group of 650 pregnant women in the second trimester of pregnancy the authors invited for subsequent clinical examination and repeated controls women with elevated antibodies against thyroid peroxidase (antiTPO) above 60 mU/l (1). The group comprised 75 pregnant women, incl. 44 (58.7%) who attended the examination. After delivery the authors examined the serum levels of TSH, fT4, antiTPO, if necessary fT3 and TRAK. RESULTS 18, i.e. 58.1% women developed post-partum thyroiditis, incl. 10, i.e. 55.6% who developed hypothyroidism and 8, i.e. 44.4% who developed hyperthyroidism. CONCLUSIONS Based on the presented study the authors recommend in pregnant women in the first trimester of pregnancy to introduce assessment of thyrotropin (TSH) and free thyroxin (fT$) and antibodies against thyroid peroxidase (antiTPO)[to detect neuropsychic sequelae on the infant after delivery. The investigation of serum levels of antiTPO antibodies will make it possible to select a group of women in risk of by the development of post-partum thyropathies which must be followed up.