Abstract Objectives: The aim of this study was to evaluate concentration of plasma fibronectin (FN) in course of pregnancy complicated by preeclampsia accompannied by diabetes mellitus and to assess whether the concentration of FN depends on the state of carbohydrate metabolism . Material and methods: The study was carried out in 2 groups: group K – consisting of 35 healthy pregnant women without complications, and group G – consisting of 12 pregnant women, 4 with gestational diabetes mellitus and 8 with pregestational diabetes mellitus, who developed preeclampsia, in course of reaserch, after 37th week of pregnancy. Concentration of FN and Fm – in order to the state of carbohydrate metabolism – was marked in the following: before 33rd week of pregnancy, between 33rd and 37th week of pregnancy and after 37th week of pregnancy. Results: No correlation between concentration of FN and duration of pregnancy in group K was found. Average concentration of FN in the subsequent periods of the pregnancy in group K were simillar and have not shown vital, statistical differences. In group G crucial statistical increase in FN concentration along with increase of pregnancy duration was found (r=0,3860, p<0,01). No correlation between concentration of FN nor Fm was found in both groups. Conclusions: The results obtained demonstrate that vascular endothelial damage, as expressed by increase in plasma fibronectin levels, is a condition specific for preeclampsia, preceding its clinical manifestation. Maternal blood concentrations of FN do not depend on the state of carbohydrate metabolism estemeted by concenatration of Fm.