Under physiological conditions, endothelial balance is shifted towards maintained vasodilation — the readiness to counteract enhanced tonus, which stems from constant stress in the circulatory system and from creation of a perfusion gradient that is responsible for tissue metabolism. Affected by different damaging factors, the endothelial cells show their lower ability to release relaxing factors while the formation of vasoconstrictor factors retains or increases, i.e. this gives rise to a state defined as endothelial dysfunction. General regularities in the production of endothelial factors are found in physiological pregnancy. The generation of endothelial factors starts changing during early pregnancy and this may be associated with the influence of factors associated with an implanted ovum. Stimulation of endothelial function in the forming fetoplacental unit is observed in the first trimester, which shows itself in the increase of constantly forming nitric oxide and prostacyclin. Starting from the second trimester, there is activation of endothelial function in the mother—placenta—fetus system, which appears as increased production of von Willebrand factor, thromboxane, and endothelin-1. Starting from the second wave of cytotrophoblast invasion (at 16—18 weeks), there are elevated serum thrombomodulin and fibronectin levels in the pregnant women, which may suggest that endothelial dysfunction syndrome develops in the fetoplacental unit even in physiological pregnancy. To date, a great amount of material has been accumulated on the role of endothelial dysfunction in the pathogenesis of preeclampsia, fetoplacental insufficiency, premature abruption of a normally situated placenta, preterm birth, and other abnormities. There is a need for in-depth, evidence-based researches that determine the significance of each factor for endothelial dysfunction, or their combinations, or ratios in the development of these or those pregnancy complications. The fact that imbalance of endothelial dysfunction markers occurs long before the clinical development of an abnormality and may determine its preclinical development stages is undoubted. This will able to timely launch preventive measures and pathogenetically sound therapy.