ObjectiveTo compare euploid and aneuploid pregnancies with respect to maternal serum and amniotic fluid (AF) levels of the components of the plasminogen system.MethodsThe study population consisted of 123 single pregnancies at the 17th gestational week, 16 with minor chromosomal abnormalities, 15 aneuploid, and 92 euploid.ResultsBoth groups with chromosomal abnormalities had significantly higher serum levels of urokinase plasminogen activator and its complexed form with its type-1 inhibitor compared with euploid pregnancies. In AF, tissue plasminogen activator was significantly lower in the aneuploid than the euploid group, whereas type-1 inhibitor of plasminogen activator was significantly higher in the cases with minor chromosomal abnormalities compared with euploid. At cutoff levels set at 100% sensitivity, the complexed form of urokinase plasminogen activator with its type-1 inhibitor had the strongest specificity (66.3%); after logarithmic transformation, its serum level was 7.53 times higher in aneuploidies than euploidies.ConclusionAneuploid pregnancies appear to be accompanied by abnormalities of the plasminogen activation system, which could lead to impaired placental perfusion and thus to abortion, fetal death, and fetal growth restriction.