Handbook of Vitamin C Research

The Role of Vitamin C in Human Reproduction 2879. Oxidative Stress and Embryo DevelopmentThe fertilization and embryo development in vivo occur in a low oxygen environment[73].This is evidenced by the increased implantation and pregnancy rates seen in ARTprocedures when antioxidant- supplemented medium is used rather than standard mediumwithout antioxidants [74]. Furthermore, addition of ascorbic acid during cryopreservationreduces the levels of hydrogen peroxide, preventing the establishment of an oxidativeenvironment in mammalian embryos [75]. Oxidative stress is implicated in defective embryodevelopment and embryo growth retardation [76, 77], due to cell- membrane and DNAdamage as well as induced apoptosis. Increased concentrations of ROS can have toxic effectson the intracellular and intercellular environment, which can result in impaired cellulargrowth in the embryo or embryo fragmentation. Subsequently, OS mediated damage ofcellular components can be harmful, as demonstrated by thalidomide induced embryopathy[73, 78]10. Preterm Labor and MiscarriageImplantation and a subsequent successful pregnancy is a very well organized process.involving complex interactions between embryo and uterine environment. Placentationincludes a series of complicated events, that result in the establishment of maternalcirculation in the placenta. During this process, OS markers are most abundant in normalpregnancies and under specific circumstances, can result in early pregnancy or recurrentpregnancy loss of unknown etiology [79, 80]. Although the role of OS in labor initiationremains unknown, a lot of studies indicate an increase of free radicals superoxide and nitricoxide as well as increased lipid peroxidation, induced by term labor [81, 82]. On the otherhand, OS may also be implicated in preterm labor, due to focal collagen damage in the fetalmembranes [34].11. Oxidative Stress and Pre-EclamsiaPre-eclampsia (PE), a pregnancy-specific condition, with an incidence of about 5% of allpregnancies and 11% of all first pregnancies is a leading cause of maternal morbidity andmortality worldwide [34]. Clinical manifestations include hypertension and proteinuria after20 weeks of gestation, in previously normotensive, non-proteinuric women [83].Consequently, PE is still a major cause of intrauterine hypoxia and growth restriction(IUGR), preterm labor, and perinatal death. Although the pathophysiology of the diseaseremains undetermined it is proposed that endothelial cell dysfunction, incomplete trophoblastinvasion and impaired placental perfusion, immune maladaptation and inflammation areinvolved. Once the diagnosis is established delivery remains the only successful therapeuticapproach [84].