Fetal and placental infection with SARS-CoV-2 in early pregnancy

Abstract

To date, mother-to-fetus transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for the coronavirus disease 2019 (COVID-19) pandemic, remains controversial. Although placental COVID-19 infection has been documented in some cases during the second- and third-trimesters, no reports are available for the first trimester of pregnancy, and no SARS-CoV-2 protein has been found in fetal tissues. We studied the placenta and fetal organs from an early pregnancy miscarriage in a COVID-19 maternal infection by immunohistochemical, reverse transcription quantitative real-time polymerase chain reaction, immunofluorescence, and electron microscopy methods. SARS-CoV-2 nucleocapsid protein, viral RNA, and particles consistent with coronavirus were found in the placenta and fetal tissues, accompanied by RNA replication revealed by double-stranded RNA (dsRNA) positive immunostain. Prominent damage of the placenta and fetal organs were associated with a hyperinflammatory process identified by histological examination and immunohistochemistry. The findings provided in this study document that congenital SARS-CoV-2 infection is possible during the first trimester of pregnancy and that fetal organs, such as lung and kidney, are targets for coronavirus. The infection and multi-organic fetal inflammation produced by SARS-CoV-2 during early pregnancy should alert clinicians in the assessment and management of pregnant women for possible fetal consequences and adverse perinatal outcomes.

Keywords: COVID-19; fetus; first trimester; miscarriage; placenta; pregnancy.

Figure 1

Presence of SARS‐CoV‐2 nucleocapsid protein, viral replicative intermediate dsRNA and virions across fetal and placental tissues. (A) Double immunofluorescence for SARS‐CoV‐2 N viral protein (green) and DAPI (blue) shows strong positivity for nucleocapsid expression (NP) in fetal lung, kidney, and placenta from SARS‐CoV‐2‐infected tissues but not for uninfected samples. (B) Double stain for dsRNA (red) and DAPI (blue) indicates RNA viral replication exclusively in fetal and placenta tissues infected with SARS‐CoV‐2. Merged images show localization of both stains. (×40 magnification, scanning zoom 3×). Scale bar represents 20 µm. (C–H) Scanning Electron Microscopy with transmitted electrons detector mode images of coronavirus particles in fetal lung and placental parenchyma. (C–E) Lung tissue with the presence of virions particles inside a vacuole. The area outlined on the upper right corner shows a large cytoplasmic vacuole with virions inside (E). (F–H) The virion particles also were present in the placental parenchyma. (G) Higher magnification of the rectangle marked in (F). The arrows point to particles consistent with the typical morphological features of coronavirus. Although postmortem changes made the good preservation of cell organelles difficult, parts of the nucleus (Nu) and the Golgi apparatus are seen. DAPI, 4ʹ,6‐diamidino‐2‐phenylindole, dilactate; dsRNA, double‐stranded RNA; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2

Figure 2

Multi‐organic fetal and placental inflammation. Histological sections with haematoxylin/eosin and immunohistochemistry from the postmortem study of fetus A and placenta showing severe inflammation. (A and B) Arrows point to inflammatory cells (macrophages and neutrophils) in the intima, media and adventitia of the arterial vessels of the heart as well as between the fascicles of the cardiac muscle cells, with several CD68‐positive macrophages (E, brown stain) (×20). (C) Fetal lung shows mild interstitial hypercellularity with inflammatory cells which express CD68 (F, arrows, brown stain) (×20). (D) Chorionic villi with active chronic intervillositis and abundant perivillous neutrophils (arrow) (×10). (G) Section of the placenta exhibiting severe inflammation with Hofbauer cells in the villous stroma strongly positive for CD163 cells (arrow, brown stain) (×10). (H) Striated muscle with inflammatory infiltrates of mononuclear cells and neutrophils, as well as edema, apoptosis, and diffuse myocyte atrophy (arrow, ×40). (I) Immunohistochemical staining for CD68 shows interstitial macrophages infiltrate in the kidney (brown stain) (×40)