During the late pregnancy and during parturition in bovine, sevearl hormones and reoxygenation of placental tissues and consequences oxidative stress were involved. In this study blood samples from pregnant cows in the last three weeks of pregnancy were taken. At parturition 10 animals were selected as normal parturition and non-retaind placental expulsion. Other 10 cows were selected with normal parturition and retaind placenta. Another blood samples were taken after 1, 24 and 48 hours postpartum from both the obivois groups. The study concluded that oxidative stress and cortisol hormone might play an important role in the process of parturition in cows. It was also found that the extra-elevation of the LPO, NO and cortisol and the reduction of antioxidants could be used as indictor for the possibility of retention of fetal membrane after parturition.