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In a first-of-its-kind report, investigators from New York City have described identification of SARS-CoV-2 RNS in placenta and membrane samples at time of delivery.
The origin of the RNA—maternal or fetal—remains unclear but the findings point to a need for more research on possible vertical transmission of the virus.
Published as a research letter in The American Journal of Obstetrics and Gynecology,1 the account reflects outcomes of polymerase chain reaction (PCR) testing of post-delivery samples from a series of women who were diagnosed with COVID-19 during pregnancy.
The deliveries occurred between March 1, 2020 an April 20, 2020 at NYU Langone Health, as recorded in the patients’ electronic health records.
The authors identified 32 COVID-positive mothers who met the criteria, of whom 11 had placental or membrane samples tested with reverse transcription PCR (RT-PCR) within 30 minutes after delivery.
Testing was done with the Cepheid Xpert Xpress SARS-CoV-2 assay. All of the women had severe to critical COVID-19 at time of delivery.
Placental swabs were taken from the amniotic surface after maternal blood has been cleared from it. Membrane samples were from between the amnion and chorion after manual separation of the membranes.
Of the 11 swabs, 3 were positive for SARS-CoV-2. None of the infants tested positive for the virus on Days 1 to 5 of life or had any symptoms of COVID-19. Seven of the deliveries were vaginal and four by cesarean; all 3 of the positive results were associated with cesarean deliveries.
Commenting on the origin of the SARS-CoV-2 RNA that was detected, the authors said it may have been maternal blood, amniotic fluid, or fetal membranes and amniotic sac. In the four infants delivered vaginally, the origin also could have been vaginal secretions.
“Although there were no clinical signs of vertical transmission,” the authors said, “the findings indicate the possibility of intrapartum viral exposure.”