Pathomorphological Changes of the Placenta in Coronavirus Disease (Covid-19) in Pregnant Women at 19-32 Weeks of Gestation

Abstract

Introduction. The morphology of the placenta (chorion) changes during pregnancy. Immature intermediate villi formed during the first two trimesters are developmental steps towards the stem villi. A cotyledon is the branching of a single stem villus into mature intermediate villi and terminal villi. Villous maturation disorders led to placental dysfunction, fetal growth retardation and intrauterine asphyxia. The formation of placental insufficiency in the case of coronavirus disease (COVID-19) in the mother in the second trimester of pregnancy prompted us to conduct this study. The choice of gestation periods in our study was related to the structural changes of the villous chorion that occur at the end of the second and the beginning of the third trimester of pregnancy. Purpose: to determine pathomorphological changes in the placenta of women who contracted COVID-19 at 19-32 weeks of gestation. Research methods. The research material is 52 placentas of live-born full-term infants whose mothers contracted the coronavirus disease, confirmed by a positive PCR test (determination of SARS-CoV-2 RNA). Group I - placentas with COVID-19 in a pregnant woman at 19-25 weeks of gestation, group II - at 26-32 weeks. The obtained results were compared with the control group (n=30; placentas of women during physiological childbirth in 2017-2018). Macroscopic, microscopic, morphometric and statistical research methods were used. Results. Chorioamnionitis was detected during microscopic examination of placentas of groups I and II: n=20 (76.9% (95% CI: 58.2%-91.3%)) and n=16 (61.5% (95% CI: 41.5%-79.7%)), p1-2=0.23; basal deciduitis: n=24 (92.3% (95% CI: 78.4%-99.4%)) and n=26 100% (95% CI: 92.9%-100%), p1-2 =0.15, respectively. The placenta with COVID-19 in the mother at 19-32 weeks of pregnancy was characterized by exudative inflammation of the basal plate: basal deciduitis (+); p1-2=0.01. The percentage of stem and mature intermediate villi in groups I and II was 42.3 [37; 47] and 24.2 [23; 26], respectively; p1-2=0.0001, with a reduced number of terminal villi in both groups – 100% (95% CI: 92.9%-100%). A deficiency of mature intermediate villi and distal villous immaturity delay of the chorion were revealed: in the group І, the percentage of fibrotic stem villi increased, with deficiency of mature intermediate villi and terminal villi ­ 16.5 [12; 21]. In the group II there are mature intermediate villi with deficiency of terminal villi ­16.8 [10; 25] against 25.6 [21; 29] in the comparison group, p<0.001. Conclusions. COVID-19 in a pregnant woman in the second and early third semesters is a risk factor for the occurrence of structural changes in the villous chorion – deficiency of mature intermediate villi and distal villous immaturity delay. Villous maturation disorders is caused by the SARS-CoV-2 coronavirus damage to the villi (endothelial necrosis, proliferative changes in the smooth muscle, obliteration of the lumen of the arterioles, fibrosis of the villus stroma) existing at the time of infection. Remodeling of blood vessels, which is prolonged in time and due to the duration and change of phases of the inflammatory process, explains the formation of chronic placental insufficiency, which can manifest itself clinically and become the cause of intrauterine hypoxia of the fetus precisely with the increase in the duration of the post-COVID interval.