[Retrospective study of the thyroid balance in pregnant women : definition of TSH and FT4 reference values]

Pregnancy leads to many physiological changes, particularly in the thyroid. This implies that the reference values of the thyroid parameters may change according to the trimesters of the pregnancy and that the management of pregnant women differs. Establishing reference values is not easy and can be done in several ways. In our study, we review the reference values of TSH and FT4 of pregnant women followed up at Liege University Hospital compared to control women. This has been achieved using retrospective data from our laboratory. We show that the small decrease in the TSH reference values in pregnant women is barely visible in a small cohort. Our FT4 values confirm what the literature shows, i.e. a slight increase during the first trimester. We emphasize the difficulty and the relevance of making reference values for pregnant women.