Abstract
A subset of placentas from pregnant women having the SARS-CoV-2 infection have been found to be infected with the coronavirus using molecular pathology methods including immunohistochemistry and RNA in situ hybridization. These infected placentas can demonstrate several unusual findings which occur together—chronic histiocytic intervillositis, trophoblast necrosis and positive staining of the syncytiotrophoblast for SARS-CoV-2. They frequently also have increased fibrin deposition, which can be massive in some cases. Syncytiotrophoblast is the most frequent fetal-derived cell type to be positive for SARS-CoV-2. It has recently been shown that in a small number of infected placentas, villous stromal macrophages, termed Hofbauer cells, and villous capillary endothelial cells can also stain positive for SARS-CoV-2. This report describes a placenta from a pregnant woman with SARS-CoV-2 that had chronic histiocytic intervillositis, trophoblast necrosis, increased fibrin deposition and positive staining of the syncytiotrophoblast for SARS-CoV-2. In addition, molecular pathology testing including RNAscope and immunohistochemistry for SARS-CoV-2 and double-staining immunohistochemistry using antibodies to E-cadherin and GATA3 revealed that cytotrophoblast cells stained intensely for SARS-CoV-2. All of the cytotrophoblast cells that demonstrated positive staining for SARS-CoV-2 were in direct physical contact with overlying syncytiotrophoblast that also stained positive for the virus. The pattern of cytotrophoblast staining for SARS-CoV-2 was patchy, and there were chorionic villi having diffuse positive staining of the syncytiotrophoblast for SARS-CoV-2, but without staining of cytotrophoblast. This first detailed description of cytotrophoblast involvement by SARS-CoV-2 adds another fetal cell type from infected placentas that demonstrate viral staining.
Highlights
The coronavirus disease 2019 (COVID-19) pandemic has continued to have a potential adverse effect on pregnant women and their infants
The novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was initially identified from pregnant women from China, it was hoped that vertical transmission of the virus would not occur, similar to previous coronavirus infections severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), and other RNA respiratory viruses [1,2]
In this report we provide immunohistochemical and molecular pathology evidence of SARS-CoV-2 staining in villous cytotrophoblast cells of the placenta which occurred in a placenta from a fetus having acquired the infection following transplacental transmission
Summary
The coronavirus disease 2019 (COVID-19) pandemic has continued to have a potential adverse effect on pregnant women and their infants. With the spread of the virus throughout the globe and additional cases of SARS-CoV-2 infection in pregnancy being reported, it became evident that a small percentage of neonates delivered to infected mothers tested positive for SARS-CoV-2 [12,13,14,15]. This raised the questions of how and when these infants had acquired their infection, whether it was vertically transmitted, and if SARS-CoV-2 could be transmitted transplacentally prior to delivery from an infected pregnant woman to her fetus [16,17,18]. In this report we provide immunohistochemical and molecular pathology evidence of SARS-CoV-2 staining in villous cytotrophoblast cells of the placenta which occurred in a placenta from a fetus having acquired the infection following transplacental transmission
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