Vertical Transmission of SARS-CoV-2 is Plausible During Pregnancy and Vaginal Delivery: A Prospective Cohort Study

Objective: To evaluate if SARS-CoV-2 is detectable in vaginal swabs and whether antibodies against SARS-CoV-2 are present in maternal and umbilical cord blood of pregnant women with COVID-19. Design: Prospective cohort study. Setting: Department of Obstetrics and Gynaecology, Copenhagen University Hospital – North Zealand, Denmark. Population: Pregnant women tested positive for SARS-CoV-2 in a pharyngeal swab between August 20th, 2020 and March 1st, 2021 who gave birth during the same period. Methods: Maternal blood sample and vaginal swabs were collected at inclusion. If included during pregnancy, these samples were repeated at delivery in addition to an umbilical cord blood sample. Swabs were analysed for SARS-CoV-2 and blood samples for SARS-CoV-2 total antibodies. Placental and neonatal swabs were performed on clinical indications. Main outcome measures: SARS-CoV-2 in vaginal swabs and SARS-CoV-2 total antibodies in maternal and umbilical cord blood. Results: We included 28 women, hereof 4 serious maternal or fetal outcomes including 1 neonatal death. Within the first eight days after a maternal positive pharyngeal swab, SARS-CoV-2 was detectable in two vaginal (2/28) and two placental swabs (2/4), whereas SARS-CoV-2 antibodies were detected in 1/13 women. After eight days, SARS-CoV-2 was not detectable in vaginal swabs and SARS-CoV-2 antibodies were observed in 19/21 of women. Antibodies in cord blood of seropositive mothers appeared after 16 days. Conclusion: Vertical transmission of SARS-CoV-2 seems plausible since SARS-CoV-2 is detectable in the vagina up to eight days after a positive pharyngeal swab at which time the neonate is not yet protected by antibodies.