The role and modulation of the oxidative balance in pregnancy.

Oxidative processes exert a fundamental regulatory function during pregnancy. It depends on the influence of oxygen, nitric oxide, reactive oxygen species and reactive nitrogen species metabolic pathways upon the vascular changes in the maternal organism, as well as on the regulation of uterine and cervical tone throughout gestation and delivery. These functions are strictly linked with the mediators of the inflammatory pathway. At the beginning of pregnancy, when a certain grade of inflammatory change is necessary to the trophoblast invasion of maternal tissue, the activation of the process by nitric oxide and reactive nitrogen species is welcome. Indeed, these products modulate the metalloproteinases, which are responsible for the remodelling of uterine extracellular matrix. At this stage estrogens are involved as well in the regulation of the delicate balance of pro-oxidant and anti-oxidant effects. Furthermore, reactive oxygen and nitrogen species appear to play an important role both in normal and pathologic embryogenesis. During advanced pregnancy, a derangement of the oxidative balance can lead to the improper activation of inflammatory changes, thus triggering premature labour as well as other complications, such as foetal growth restriction and preeclampsia. Although a number of pro- and anti-oxidant agents are available to influence the above-mentioned processes, there is no way to adequately measure the oxidative needs in single cases, in order to modulate the oxidative balance in clinical practice. Pharmacological research should be addressed to the development of new drugs, as well as to selective methods of delivery to the gestational tissues.