Abstract
Introduction: Coronavirus disease 2019 (COVID-19) is a risk factor for developing placental dysfunction when a pregnant woman is infected before 35 weeks of gestation. According to our previous studies, no cases of antenatal asphyxia were observed when infection occurred after this gestational age. The children were born with high Apgar scores and negative PCR tests for SARS-CoV-2 RNA from women who had clinical manifestations of COVID-19 confirmed by a positive PCR test.
Objective of the Study: To investigate the pathomorphological changes in the placenta during full-term pregnancy in the acute phase of COVID-19 in women.
Materials and Methods: The placenta (n=37) was studied at the birth of a live full-term fetus (main group) and compared to placentas from physiological deliveries before the COVID-19 pandemic (n=38, comparison group). Comprehensive morphological methods were used, including macroscopic, microscopic, immunohistochemical, electron-microscopic, morphometric, and statistical.
Results: Structural changes were noted in the syncytiotrophoblast of the placenta, including loss of microvilli, nuclear membrane invaginations, appearance of cytoplasmic vacuoles, apoptosis, and chromatin condensation. In the endothelium, apoptosis, swelling, and mitochondrial homogenization were observed. Spherical structures similar to viral particles with an electron-dense membrane were found extracellularly, outside the fibroblast. The structural features indicated endothelial dysfunction and circulatory disorders – 97.3% (95% CI: 89.4%–100%); placentitis – 100% (95% CI: 94.6%–99.5%). Swelling of the chorionic villi was observed in 97.3% (95% CI: 89.4%-100%), with the percentage of stroma in the terminal villi increasing to 71.1 [49.5; 85.1] compared to 32.6 [26.2; 39.5] in the comparison group (p < 0.0001). A reduction in the percentage of vessels in the terminal villi was noted due to a decrease in lumen size – 29.9 [14.5; 51.2] compared to 67.4 [58.7; 73.8] in the comparison group (p < 0.0001); and a reduction in the percentage of the intervillous space to 21.7 [12.9; 33.1] compared to 44.2 [40.3; 49.7] (p < 0.0001).
Conclusions: In the acute phase of COVID-19, pathomorphological changes were observed in the placenta, indicating endothelial dysfunction caused by SARS-CoV-2. This was manifested by circulatory disorders, swelling of the stroma of the chorionic villi with a reduction in capillary lumen size and the percentage of free intervillous space, and inflammatory infiltration, leading to maternal and fetal malperfusion in the placenta. In our opinion, pathology changes in the structures forming the vasculosyncytial membranes were compensated by the already-formed placenta with sufficient terminal villi and local placentitis (limited to one cotyledon). Apoptotic changes in the syncytiotrophoblast and endothelium are morphological manifestations of hypoxia and energy deficiency in the placenta. These changes require further investigation in the context of the prolonged post-COVID interval in pregnant women infected with the SARS-CoV-2 virus during the second trimester.