Trophoblast Damage with Acute and Chronic Intervillositis: Disruption of Placental Barrier by SARS-CoV-2.

Abstract Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was demonstrated in placenta; however, the data on the prevalence of placental infection and associated histopathology are limited. In order to identify the frequency and features of SARS-CoV-2 involvement we performed a clinicopathologic analysis of 75 placental cases from women infected at the time of delivery and 75 uninfected controls. Placental samples were studied with anti-SARS-CoV-2 immunohistochemistry (IHC) and/or in situ hybridization (ISH). Positive results were confirmed by electron microscopy (EM) and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). During delivery only one women had symptoms of COVID-19, six women reported previous symptoms, and 68 women were asymptomatic. All neonates tested negative for SARS-CoV-2 by nasopharyngeal swab PCR. Obstetric histories were unremarkable in 29 of 75 positive and 8 of 75 negative women. Respectively, placental examination was normal in 12 of 75 infected and 3 of 75 uninfected subjects. In the remaining cases placental pathology correlated with obstetric comorbidities without significant differences between positive and negative women. SARS-CoV-2 was identified in one placenta of an infected, but asymptomatic parturient. Viral staining was predominantly localized to the syncytiotrophoblast (STB) which demonstrated marked damage accompanied by perivillous fibrin deposition and mixed intervillositis. A significant decrease of viral titers was detected in the attached umbilical cord comparing to the villous parenchyma by qRT-PCR. SARS-CoV-2 is seldom identified in placentas of infected women. Placental involvement by the virus is characterized by STB damage disrupting placental barrier and can be seen in asymptomatic mothers without evidence of vertical transmission.