Changes in the levels of lipoperoxide and antioxidant factors in human placenta during gestation.

The concentration of lipoperoxides in maternal blood increases as gestation progresses. The concentration in pregnant women at 40 weeks gestation is 1.6 times higher than in nonpregnant women. The concentration in the cord blood, however, is 70% lower than that in maternal blood. To study the role of placental tissue in the difference in the lipoperoxide concentration between the cord blood and maternal blood, we investigated the lipoperoxide concentration, antioxidant activities and in vitro lipoperoxide formation in placental tissue during pregnancy. The lipoperoxide concentration was 50% lower in placental tissue of 40 weeks gestation than in tissue of 5-11 weeks gestation. Catalase and superoxide dismutase activities in placental tissues increased as gestation progressed, while glutathione peroxidase activity and alpha-tocopherol concentration did not change significantly during the gestational period. The in vitro formation of lipoperoxides in placental tissue decreased as gestation progressed. These results show that placental tissue suppresses lipoperoxide formation in the late gestational age, lowers the concentration of lipoperoxides in the blood and protects the fetus against oxygen toxicity.