ABSTRACT
Background: Evidence has shown that pregnancy is a risk factor for severe illness in women with SARS-CoV-2 (COVID-19). Yet their newborns are mostly doing well. The placenta is a complex, highly specialized, but poorly understood organ. The COVID-19 infection related specific pathological changes in placenta and prevalence of transplacental transmission of COVID-19 has not been fully explored and validated. Design: Universal screening for COVID-19 among all pregnant women on admission to labor and delivery unit was initiated in April 2020 at our institute. With IRB approval, 54 term pregnant women with positive COVID-19 nasopharyngeal swap results at admission during April 2020 to Jun 2021 were recruited. Patients' demographic characteristics and clinical presentation were summarized in Table 1. Histopathology of all placentas was independently reviewed by two board certified pathologists. RNA was extracted from Formalin-Fixed Paraffin-Embedded (FFPE) blocks of 15 randomly selected placentas. ThermoFisher TaqPathTM SARS-CoV-2/COVID-19 RT-PCR assays were performed to detect the presence of the virus with proper controls. Results: Hispanic or Latino pregnant women represented 39% of the study cohort tested positive for COVID-19 at admission, followed by American Africa (26%) and Caucasian (17%). Most patient were overweight before pregnancy and 1/3 patients had at least one comorbidity. Majority patients (72%) were completely asymptomatic. The rest of patients had somewhat mild symptoms including sore throat, cough, low-grade fever, and/or loss of taste/smell. All deliveries were term. All neonates were in healthy status at birth. No suspected vertical transmission was observed. Histopathological inspection of placentas showed nonspecific features of maternal or fetal vascular malfunction and inflammation (Table 2). Among 15 placental samples tested, no SARS-CoV-2 virus was detected. Conclusions: Multiple studies indicated that only a very small proportion of neonates delivered to mothers with COVID-19 infection were also tested positive for COVID-19. Our data suggested that COVID-19 infected mothers who were asymptomatic or only with mild symptoms at labor unlikely vertically transmit the virus through the placenta. This finding may ease the anxiety of asymptomatic mothers caused by positive COVID-19 test result at delivery admission. (Table Presented).