Histological and immunohistochemical features of the placenta associated with COVID-19: a systematic review and meta-analysis

Abstract

Aim: To make a systematic review and meta-analysis of published data on the study of histological and immunohistochemical features of the placenta in women who had acute coronavirus infection associated with SARS-CoV-2 (“Covid” placentas) during pregnancy. Materials and Methods: The search for literature data is based on the PRISMA methodology); the MEDLINE database (PubMed®) was searched using Medical Subject Headings terms from January 2020 to July 2023. The project was registered in the Open Sience Frame (Project Identifier: DOI 10.17605/OSF.IO/GDR3S, Registration DOI: https://doi.org/10.17605/OSF.IO/H2KPU). Preference was given to studies in which the description of placentas met the requirements of the Amsterdam Placental Workshop Group Consensus Statement. Results: A total of 31 studies were included; the number of participants whose morphological and histological description of the placentas could be subjected to meta-analysis was 2401, respectively, in the group with a “Covid” history and 1910 – conditionally healthy pregnant women. Pathological changes in the placental complex were not detected in 42±19.62% of pregnant women with a history of Covid. Immunohistochemical examination of placentas preferably focuses on the detection of SARS-CoV-2 spike protein or ACE2. According to currently available studies, in the placentas of women who have had COVID-19 during pregnancy, there are no pathognomic histological patterns specific to this infection and direct damage to the placenta is rarely observed. Histological patterns in “covid” placentas are isolated, most often a combination of lesions in both the maternal and fetal malperfusion. Conclusions: According to currently available studies, in the placentas of women who have had COVID-19 during pregnancy, there are no pathognomic histological patterns specific to this infection and direct damage to the placenta is rarely observed. The probability of infection of the intrauterine fetus by the transplacental hematogenous route is the lowest compared to other routes, which, in our opinion, is a possible explanation for the high frequency of MVM without subsequent infection of the fetus.