A sufficient amount of iodine in food is necessary for the thyroid gland to produce hormones during pregnancy. The aim of our work was to evaluate iodine and thyrotrophic hormone (TSH) concentration in urine, free triiodothyronine (fT3) and thyroxine (fT4) in complicated pregnancies in Upper Silesia (region of iodine deficiency in Poland) in comparison with normal pregnancies. In both groups the iodine content in urine was evaluated by a quick test and serous concentrations of TSH, fT3 and fT4 were determined by a radioimmunological method. We found the iodine excretion with urine below 100 microg/L in 29.15% of all women under study, i.e. an insufficient supply of this element. The reduced iodine concentration in urine was found to be more often in women with imminent premature delivery. Moreover, it was found that in II trimester the concentration of iodine excreted with urine had been significantly lower comparing to the patients examined in III trimester. We found significantly higher concentration of thyrotrophic hormone in pregnant women with iodine excretion below 100 microg/L of urine. Evaluation of the iodine concentration in urine may be a simple screening test to determine the supply of this element in a diet. Moreover, our studies demonstrate the necessity for the iodine supplementation in pregnant women in the Silesian region--an area of iodine deficiency in Central Europe.