Acute herpes simplex virus infection in pregnant women results in intrauterine infection of the fetus in 45–50% of cases, thus being the cause of septic complications and severe somatic and neurological disorders in the newborn.The aim of the study was to investigate the placentas of new mothers with newly diagnosed herpes simplex virus type 2 infection (HSV-2) using histological and immunochemical methods.Material and methods. This histological study included 10 placentas of new mothers after operative delivery by caesarean section with newly diagnosed HSV-2 infection. The comparison group (control) consisted of 10 placentas of women with a physiological pregnancy. Histological sections of the placenta were stained with hematoxylin and eosin, Giemsa's solution and Picro-Mallory staining. Identification of the pro- and antiinflammatory phenotype of macrophages (CD68, CD163), subpopulations of CD4 and CD8 lymphocytes, TLR4 receptor expression was performed by immunohistochemical method using specific antibodies. Quantification of the cell population and TLR4 receptors was performed morphometrically. The data obtained were statistically analysed using MS Excel (2016) and SPSS Statistics 17.0.Results. Morphological manifestations of acute herpes simplex virus infection were combined inflammatory and compensatory in nature in the third trimester of pregnancy. The histological picture of the fetal part of the placenta demonstrated a decreased number of M2 (antiinflammatory) macrophages and an increased number of M1 (pro-inflammatory) macrophages. The imbalance between CD163+ and CD68+ profiles of placental macrophages with the numerical predominance of the latter evidenced a pronounced cellular immune response; this, in turn, was supported by intense TLR4 immunopositive staining of the fetal part of the placenta. There was perivillous fibrin deposition of varying degrees, villus agglutination, and necrosis of trophoblast cells associated with a relatively small population of CD4+ and CD8+. Villitis of viral etiology was characterized by destructive infiltration of maternal CD8+ T-lymphocytes penetrating the chorionic villi, combined with activated macrophages in the villi of the fetal part of the placenta. Modifications in the proportion of immune cells during HSV-2 infection supported cytotoxic and autoimmune reactions in the placenta in response to HSV-2 introduction.Conclusion. The results obtained evidence the development of a pronounced immunopathological process in the tissues of the fetal part of the placenta, which results in the decreased protective and compensatory properties of the placenta and increases risk of perinatal complications.