Micronuclei (MN) in cells undergoing mitosis arise from structural chromosomal aberrations or disturbed function of the mitotic spindle. Some authors consider that MN frequencies in peripheral blood lymphocytes of human individuals provide an effective estimate of the effects of physical and chemical factors [1]. This test permits an analysis of a great number of lymphoblasts per sample, which is important for a more realistic picture of the cell’s cytogenetic damage, as well as for the discovery of genotoxic effects in tested preparations [2-4]. In previous papers [5,6], we have shown that gestagens (progesterone and its derivatives) induce a significant increase of MN frequency in female patients who maintained their pregnancies by taking these preparations, as well as in their newborns.

Progesterone and its derivatives are a significant group of medicines with an important application in the prevention of spontaneous abortions. A considerable quantity of progesterone changes the ultrastructure of uterus muscles, and in this way inhibits spontaneous contractions and the possibility of abortion [7]. Since they are frequently used, and their activity is realized by direct influence on DNA molecules [8], the need arises to test these preparations for genotoxicity. The aim of this study was the determination of average MN frequency in dependence on gestagen type, as well as to show variability of frequencies of this phenotypical characteristic by the application of analysis of variance (ANOVA).