Expressive deficiency of iodine (level of iodine in the urine is under 50 mg/l) is characteristic for 10% children and 20% adult. Low levels of iodine in the urine were described by women after the delivery and by newborns. In the article are described specificity physiology of the thyroid gland, consequences of low intake of iodine, importance and risk of supplementation of iodine in the pregnancy. Intake of dose 200 mg iodine per day for pregnant women is important as the prevention of pathophysiological changes in the pregnancy and for development of foetus.

        Key words: iodine, pregnancy, thyroid gland, supplementation