COVID-19: relationship between macro- and microvascular changes in the placenta and pregnancy complications
Authors:   Almazov National Medical Research Centre, Rudenko K.A. ,   St. Petersburg, Russian Federation, Roshchina T.Yu. ,   Almazov National Medical Research Centre; St. Petersburg, Russian Federation, Stenyushkina A.L. ,   Almazov National Medical Research Centre; St. Petersburg, Russian Federation, Zazerskaya I.E. ,   Almazov National Medical Research Centre; St. Petersburg, Russian Federation
Published: November 2024

Abstract Aim. To present current data on morphological, including vascular, changes in the placenta of patients with COVID-19, as well as their relationship to gestational complications and perinatal outcomes. Key points. The placenta is one of the possible targets for coronavirus infection due to the presence of SARS-CoV-2-tropic structures in its cells: the transmembrane angiotensin-converting enzyme 2 receptor and the serine protease TMPRSS2. The impact of coronavirus infection on the placental morphology is still a controversial issue. The most common pathological changes in the placental structures in patients with current or previous COVID-19 are signs of maternal and fetal malperfusion, such as decidual arteriopathy with atherosis and mural hypertrophy of vessels, increased fibrin deposition and thrombus formation in the intervillous and subchorionic space, as well as in the chorionic plate, accelerated villous maturation with increased formation of syncytial knots, the formation of retroplacental hematomas and villous infarctions, chorangiosis and vascular ectasia. Significant placental vascular remodeling has been observed in COVID-19 patients due to smooth muscle cell proliferation and mural fibrosis. In addition, in some cases, signs of severe acute or chronic inflammation of placental tissues have been detected. It is assumed that the severity of coronavirus infection plays an important role in the severity of placental morphological changes, especially with regard to endothelial dysfunction and clottage, but this hypothesis remains controversial. Placental abnormalities, particularly vascular, are associated with pregnancy complications such as preeclampsia, preterm birth, antenatal death and neonatal morbidity. Late SARS-CoV-2 strains have a significant impact, as the adverse outcomes, including stillbirth and preterm birth, have increased with the emergence of variants of concern, including the Delta strain. At the same time, an increased incidence of maternal vascular malperfusion has been observed in the placenta. The concept of coronavirus placentitis is introduced — a placental pathology detected in cases of stillbirth in patients with coronavirus infection that represents a combination of increased fibrin deposition in the intervillous space, chronic histiocytic intervillositis and trophoblast necrosis, which leads to total diffuse destruction of the placental parenchyma, inability to perform its respiratory function and, as a consequence, fetal death or neonatal complications. The possible beneficial effect of low molecular weight heparins and acetylsalicylic acid on vascular disorders in the placenta and, accordingly, the fetal condition is discussed. Conclusion. Most authors agree that the most common pathological changes in the placentas of patients with COVID-19 are signs of maternal and fetal malperfusion. These disorders are not strictly specific and are observed in patients with severe endothelial dysfunction and associated gestational complications, such as preeclampsia and fetal growth restriction. It seems that the placenta in COVID-19 is a reflection of mother’s systemic endothelial dysfunction and microcirculation disorders. It is no question that the identified vascular changes negatively affect perinatal outcomes and the incidence of pregnancy complications, but this association requires further study. Key words: COVID-19, placenta, coronavirus disease, preeclampsia, malperfusion.