Context: Over the past 15 years there have been discussions about advisability of thyroid gland function screening in pregnant women, recommendations are being defined at least ten years. The reasoning is based on fact, that not only complications in pregnancy or after delivery were proved, but also problems in mental development of children, the mothers of which suffered impairement of thyroid gland function. Objective: We are presenting thyroid parametres TSH, TPOAb, in part also FT4, in 1st trimestr of pregnancy. Examination were performed in three Czech centers and included 4500 pregnant women. Results: The TSH suppression was proved in 3.6%, mostly without link to thyroid gland function, the increased TSH concentration in connection with (sub)clinical hypothyroidism was found in 5% of women, the low FT4 concentration under 9.8 pmol/l, which endangers fetal intellectual development, was found in 17 of 120 investigated woman with TSH higher than 4.00 mU/l. Thus exists a risk of minimum 1 to 170 in all group, that insufficient fetal brain development occurs. TPOAb were positive in 15% women. Increased risk of thyroid malfunction progress in women with positive TPOAb in pregnancy (and up to 50% after delivery) was repeatedly proved. Conclusion: Based on the results (5% hypothyroidism, 15% with TPOAb pregnant women) we would like to commence discussion concerning screening in pregnancy in CR, preferably before the planned conception, or at latest just before the actual pregnancy. Systematic cooperation among gynecologists, endocrinologists, general practitioners and laboratories should be established to solve the problems, as laboratory normal range, pregnancy timing for examination, unification of diagnostic procedures and correct interpretation of the results.

        Key words: hypothyroidism, pregnancy, screening, thyroid gland, TSH