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Vitamin A and pregnancy: myths and reality; prospects for the use in patients with endometriosis. A review

BACKGROUND: Retinol in its various forms, being a powerful antioxidant, has a multifaceted effect on the functioning of body systems. Replenishment of the daily requirement for the vitamin is possible only when it is supplied from outside sources. Both excess intake and deficiency of retinol are associated with adverse effects. 
AIM: The aim of this study was to assess the role of vitamin A in the functioning of the female reproductive system, its effect on pregnancy, and the prospects of using it as a pathogenically justified therapy for endometriosis. 
MATERIALS AND METHODS: We performed this review, analyzing articles from such electronic databases as PubMed, ScienceDirect, and Cyberleninka, published in the period from 2000 to 2020. 
RESULTS AND CONCLUSIONS: Vitamin A plays an important role in pregnancy; its deficiency is associated with a number of malformations, the risk of respiratory distress syndrome and disorders of the immune system development in the fetus. Despite the alleged risk of using vitamin A in pregnant women, it can be prescribed both at the planning stage and during pregnancy in safe therapeutic doses, up to 10,000 IU / day, in order to reduce the number of congenital malformations, to give birth to children with higher Apgar scores, and to prevent anemia. Retinol has antiproliferative and antitumor effects and affects the biosynthesis of estrogens, which justifies the possibility of its involvement in the pathogenesis of genital endometriosis. Given the ability of vitamin A to inhibit the proliferation of endometrioid ovarian cysts, to reduce the size of endometrioid heterotopias, and to modulate the synthesis of proinflammatory cytokines, it can be considered as a perspective therapy in the combined treatment of genital endometriosis.