The objective of the present study was to evaluate effects of iron deficiency anemia in pregnant women on the effectiveness of iodine prophylaxis; the secondary objective was to develop standard prophylactic iodine dose schedule for these patients. The study included two groups of pregnant women treated either with a daily dose of 200 mcg potassium iodide (group 1, n=32) or with 300 mcg potassium iodide/day (group 2, n=68). In all of them, blood TSH, free thyroxin and antithyroid peroxidase antibody levels were measured along with iodine excretion in urine. Thyroid volume was determined by ultrasound. Diagnosis of anemia was based on the results of clinical blood analysis including hemoglobin level, erythrocyte count, hematocrit, and mean hemoglobin content of red blood cells. Iron deficiency was estimated from serum iron and ferritin (SF) levels. Treatment with potassium iodide during pregnancy resulted in a significant increase of the median urine iodine level to 260.9 mcg/l and 143.7 mcg/l in groups 1 and 2 respectively (p<0.05). It means that iodine excretion in urine during pregnancy is directly related to the efficiency of prophylaxis; it is optimal in women consuming daily at least 300 mcg of potassium iodide. Of all hematological parameters, the serum ferritin level undergoes the largest deviation (decrease) from the normal value. It was below 15 ng/ml in 24 (31.2%) patients with the median urine iodine level of less than 150 mcg/l and in 10 (11.1%) patients with the median urine iodine level higher than 150 mcg/l (a three-fold difference).