Placental Privilege: Evidence of organ resilience in severe COVID-19 in pregnancy

Background: COVID-19 infection in pregnancy is associated with preterm birth and an increased risk of severe disease, needing intensive care admission for management of maternal multi-organ failure. The placenta, a fetal organ, functions as a barrier at the maternal interface and expresses the SARS-CoV-2 viral receptors. However, placental infection and transplacental transfer of virus are rare, suggesting placental resistance to viral infection. Here, we seek to determine the impact of severe COVID-19 infection on maternal, newborn, and placental outcomes. Methods: A prospectively recruited cohort of pregnant COVID-19 patients (n = 204) at a quaternary perinatal academic center were retrospectively analyzed. During pregnancy umbilical artery (UA) Doppler assessment was performed to assess placental function. At delivery, maternal and fetal outcomes were assessed, with paired maternal peripheral blood and placenta samples collected (n = 26) for bulk RNA sequencing (RNA-seq). Post-sequencing analysis with single cell deconvolution and pathway analysis was performed. Results: Maternally-indicated preterm births were more frequent in severe, but not asymptomatic or mild/moderate COVID-19 infection. In severe COVID-19 infection, UA Doppler assessment was normal. Rates of fetal growth restriction and placenta:birth weight ratios were similar between groups. RNA-seq showed a distinct adaptive immune activation signature in peripheral blood while placental transcripts showed no significant changes in immune cell types. Conclusion: Despite multi-organ failure, severe COVID-19 did not significantly impact placental function and transcriptomics with iatrogenic preterm birth indicated for maternal-indications.