In healthy and complicated pregnant cows, on the 2 nd and 6 th months of pregnancy in order to determine the levels of maternal serum Paraoxonase 1 (PON1) activity and the possibility of complications can occur during the pregnancy might be a premise indication. Serum samples were taken at 2 nd and 6 th months of 252 pregnant cows at the end of their pregnancies. The cows were classified into two groups such as complicated (Abortion, Dystocia) and non-complicated. Maternal serum PON1 activity in 6 th months was lower at complicated group than normally pregnant group (P=0.004; P<0.01), no difference was discovered between these groups in their 2 nd month of pregnancy (P>0.05). Among the concentration of HDL, TP and globulin no statistical difference was observed between complicated, subgroups and normal births (P>0.05). Levels of PON1 in 2 and 6 months were statistically different between the groups of dystocia and normal pregnancy (P<0.01; P = 0.003), and abort and normal pregnancy (P<0.05; P=0.033). In this study, it was inferred that the evaluation of PON1 activity early indicator of complications for clinicians that might occur in further periods of pregnancy. These results showed the fact that PON1 activity can be used as a marker relatively at the early phases of pregnancy in complicated cows.