The impact of SARS-CoV-2 infection at different stages of pregnancy on placental inflammatory responses

Background The specific impact and pathology of SARS-CoV-2 infection on maternal and fetal health have not been comprehensively investigated. Therefore, we investigated the inflammatory response of fetal tissues in pregnant women infected with SARS-CoV-2 at different stages of pregnancy. Methods We collected placenta samples from 52 patients at Tai’an Central Hospital, who underwent delivery between November 2022 and September 2024. We analyzed general patient data and maternal-fetal outcomes and conducted histological observations using HE staining. Furthermore, we used ELISA to quantitatively analyze the concentration of IL-6 in umbilical cord blood and amniotic fluid. Additionally, Western blot analysis was conducted to evaluate the expression levels of TNF-α and IL-1β in the placental tissues. Results Among participants, 33 pregnant women were diagnosed with SARS-CoV-2 infection. Patients infected SARS-CoV-2 during mid-pregnancy developed thrombosis, stromal protein deposition, and villous interstitial inflammation compared to the control group (P < 0.05). However, No significant placental pathology differences were found between late-term stages with the control group (P > 0.05). Western blot analysis revealed elevated TNF-α and IL-1β levels in infected placental tissues, with no significant difference between mid-term and late-term pregnancies. IL-6 levels in amniotic fluid showed no significant difference, and IL-6 expression was not detected in umbilical cord blood. Conclusion SARS-CoV-2 infection during pregnancy appears to have limited impact on overall maternal and fetal outcomes. However, the infection may lead to inflammatory changes in placental tissues, particularly during the mid-trimester. These findings suggest the importance of careful monitoring and management of SARS-CoV-2 infection in pregnant women. Nonetheless, larger studies are necessary to confirm these observations and explore the long-term effects on both maternal and fetal health.