Abstract: Some of reactive oxygen species (ROS) were produced in the microenvironment of oocyte and embryo when oxygen participates in the metabolism. If not eliminated in time, ROS can directly induce the oxidative stress. Studies have shown that the oxidative stress is one of the dominant factors related to the oocyte quality. The excess oxidative stress may lead to changes in the morphology and function of mitochondria in the oocyte, the synthesis of ATP and the meiotic process. After that, the increasing oocyte aneuploidy and the damage of embryonic DNA may lead to the stagnation of embryonic development and the poor outcome of pregnancy. In in vitro culture of oocyte and embryo, the adverse effects of oxidative stress can be well eliminated by adding exogenous antioxidants or free radical scavenger, and establishing and maintaining the hypoxic environment for the development of oocyte and embryo. This article reviewes the onset of oxidative stress, the effect on the development of oocytes and embryo and the mechanisms involved, and how to overcome the adverse affect of oxidative stress.

Key words: Reactive oxygen species, Oxidative stress, Oocytes, Fertilization in vitro, Embryo transfer, Pregnancy outcome