COVID-19-related inflammation of the placenta impedes fetal development in pregnant hamsters.

Pregnant women are at higher risk of severe COVID-19, with vaccine access and hesitancy remaining a challenge. Here, we use a pregnant female hamster model of COVID-19 to explore the effects of maternal infection on pregnancy, revealing a significant increase in intrauterine growth restriction (IUGR) due to placental inflammation. Viral infection causes bronchopneumonia and weight loss in infected dams, but no vertical transmission occurs. IUGR is instead linked to placental damage, characterized by fibrin deposition, thrombosis, and elevated placental expression of IP10, IL6, and IL10, irrespective of fetal sex. Enoxaparin treatment reduces placental damage and improves fetal outcomes, while vaccination enhances viral clearance, protects the placenta, and reduces the risk of IUGR. These findings underscore placentitis as a key driver of fetal complications upon SARS-CoV-2 infection and highlight the potential of vaccination and anticoagulant therapy to protect both mother and child.