Introduction: Iodine deficiency in pregnant women, even of a mild degree, may have adverse effects on both the mother and the foetus. Despite the obligatory model of functioning iodine prophylaxis in Poland, the iodine supply in women during pregnancy and physiological lactation is insufficient. Therefore, those groups should take additional iodine supplementation at a dose of 150–200 μg/day. The aim of this study was to examine the effectiveness of iodine prophylaxis in pregnant women in Poland.

Material and methods: The assessment of iodine supply, urine iodine concentration (UIC) in the spot urine sample, as well as levels of TSH, fT4, thyroid antibodies, and thyroid volume, was performed at one time point in 115 women (7 in the 1st trimester, 61 in the 2nd trimester, and 47 in the 3rd trimester).

Results: Only 45.2% of women were taking additional amounts of iodine at any time of pregnancy, and the median ioduria was 79.6 μg/L, which pointed to an insufficient supply of iodine. The percentage of women using iodine supplementation increased with the length of pregnancy, which indicates that the recommendations are implemented too late. In women who took iodine supplementation, ioduria was significantly higher than in those not applying iodine supplementation (median 129.4 μg/L vs. 73.0 μg/L; p < 0.001); however, this was still below recommended values.

Conclusions: The effectiveness of iodine prophylaxis in pregnant women in Poland, evaluated on the basis of the analysis of randomly chosen sample, is not satisfactory in terms of compliance with the recommendations and, possibly, the quality of supplementation. (Endokrynol Pol 2015; 66 (5): 404–411)