The influence of SARS-CoV-2 on the immune system elements and on the placental structure. Clinical, histological and immunohistochemical study

Background: The effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy remain relatively unknown. Aim: We present this original paper where we analyzed 60 parturients, at term, 30 without associated infection (C-) and 30 with associated infection (C+), present at birth. Methods: We analyzed the blood count and placental microscopic structure through classical and immunohistochemical staining and observed the placental areas affected by the presence of SARS-CoV-2. Results: SARS-CoV-2 infection was accompanied by a decrease in the number of lymphocytes, the number of platelets and the presence of placental structural changes, identifying extensive areas of amyloid deposits, placental infarcts, vascular thrombosis, syncytial knots, with a decrease in placental vascular density and the presence of infection in the cells located at decidual level, at syncytiotrophoblast level and at the level of the cells of the chorionic plate, still without overcoming this barrier and without causing any fetal infection in the analyzed cases. Conclusions: This study shows that the invasion of SARS-CoV-2 in the placenta can produce significant structural changes, with a decrease in placental vascular density that can have significant implications on proper fetal perfusion. Also, the presence of immunoreactivity at the level of decidua, the placental villi, as well as the chorionic plate proves that the virus can overcome the maternal-fetal barrier. However, in the analyzed cases there were no fetal infections at birth, which may show that local placental factors can be a protective filter for the fetus.