Evaluation of vertical transmission of SARS-CoV-2 in utero: nine pregnant women and their newborns

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), mainly transmitted by droplets and close contact, has caused a pandemic worldwide as of November 2020. According to the current case reports and cohort studies, the symptoms of pregnant women infected with SARS-CoV-2 were similar to normal adults and may cause a series of adverse consequences of pregnancy (placental abruption, fetal distress, epilepsy during pregnancy, etc.). However, whether SARS-CoV-2 can be transmitted to the fetus through the placental barrier is still a focus of debate. Methods In this study, in order to find out whether SARS-CoV-2 infect fetus through placental barrier, we performed qualitative detection of virus structural protein (spike protein and nucleoprotein) and targeted receptor protein (ACE2, CD147 and GRP78) expression on the placental tissue of seven pregnant women diagnosed with COVID-19 through immunohistochemistry. Amniotic fluid, neonatal throat, anal swab and breastmilk samples were collected immediately in the operating room for verification after delivery, which were all tested for SARS-CoV-2 by reverse transcriptionpolymerase chain reaction (RT-PCR). Results The result showed that CD147 was expressed on the basal side of the chorionic trophoblast cell membrane and ACE2 was expressed on the maternal side, while GRP78 was strongly expressed in the cell membrane and cytoplasm. The RT-PCR results of Amniotic fluid, neonatal throat, anal swab and breastmilk samples were all negative. Conclusions We believed that despite the detection of viral structural proteins in the placenta, SARS-CoV-2 cannot be transmitted to infants due to the presence of the placental barrier. Summary Our results showed that, excluding environmental pollution after birth and vaginal infection during childbirth, SARS-CoV-2 was less likely to be transmitted vertically in utero.