Placental Morphogenesis Following Third-Trimester SARS-CoV-2 Infection

The aim of the study is to identify the features of placental morphogenesis in women who had COVID-19 of varying severity during the third trimester of pregnancy. Material and methods. A single-center retrospective study was conducted for the period from March 2020 to April 2022. Using a continuous sampling method, 148 medical records and histological specimens taken from the central part of the placenta were selected from women who had contracted COVID-19 during the third trimester of pregnancy. The entire sample was divided into three comparison groups: Group 1 – mild course of viral infection (n=77), Group 2 – moderate course (n=52), Group 3 – severe course (n=19). The severity of the illness caused by the COVID-19 viral infection was assessed according to the criteria outlined in the Clinical Protocols "Organization of Medical Care for Pregnant Women, Parturient Women, Postpartum Women, and Newborns with the Novel Coronavirus Infection COVID-19," Versions 3 and 5. Histopathological examination of the placentas was performed in accordance with the clinical guidelines of the Russian Society of Pathologists, "Rules for Pathological Examination of the Placenta" (2017). Results. A severe course of coronavirus infection increases the odds of placental hemodynamic disorders by 4.5 times (95% CI 1.58–13.17). Light microscopy analysis of the placentas revealed a higher frequency of maternal malperfusion in the severe infection group – 10 cases (52.6%) – compared to the moderate group – 11 cases (21.2%) – and the mild group – 5 cases (7.8%) (p<0.001). The frequency of inflammatory changes in the placenta with intact fetal membranes was more commonly identified in severe infection – 6 cases (31.6%) – versus 4 cases (7.7%) in moderate disease (p<0.001). Conclusions. Maternal malperfusion, specifically of the accelerated villous maturation type, was more frequently observed in cases of severe coronavirus infection. Among patients with a severe course of SARS-CoV-2 infection without premature rupture of membranes, inflammatory changes in the placenta were detected four times more often than in patients with a moderate disease course. These findings confirm an increased frequency of placental pathology in the third trimester of pregnancy associated with persistent SARS-CoV-2 infection in severe cases. This persistence leads to stromal-vascular disorders and vascular insufficiency, posing a risk of adverse outcomes for both the mother and the fetus.

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