The association between maternal COVID-19 infection, placental histomorphology and perinatal outcomes is uncertain. The published studies on how placental structure is affected after SARS-CoV-2 virus in COVID-19-infected pregnant women are lacking. We investigated the effects of maternal SARS-CoV-2 infection on placental histomorphology and pregnancy outcomes. A retrospective cohort study on 47 pregnant women with confirmed SARS-CoV-2 infection, matched with non-infected controls, was conducted. Relevant clinicopathological data and primary birth outcomes were recorded. Histomorphology and SARS-CoV-2 immunohistochemistry analyses of placental tissues were performed. Only 1 of 47 cases showed SARS-CoV-2 immunoreactivity in the syncytiotrophoblasts. Histologically, decidual vasculopathy (n = 22/47, p = 0.004), maternal vascular thrombosis (n = 9/47, p = 0.015) and chronic histiocytic intervillositis (n = 10/47, p = 0.027) were significantly higher in the COVID-19-infected placentas when compared to the control group. Maternal vascular thrombosis was a significant feature in the active COVID-19 group. A significant lower gestational age (p < 0.001)) at delivery and a higher caesarean section rate (p = 0.007) were observed in the active SARS-CoV-2-infected cases, resulting in a significant lower fetal-placental weight ratio (p = 0.022) and poorer Apgar score (p < 0.001). Notably, active (p = 0.027), symptomatic (p = 0.039), severe-critical (p = 0.002) maternal COVID-19 infection and placental inflammation (p = 0.011) were associated with an increased risk of preterm delivery. Altered placental villous maturation and severe-critical maternal COVID-19 infection were associated with an elevated risk of poor Apgar scores at birth (p = 0.018) and maternal mortality (p = 0.023), respectively.
Keywords: COVID-19; SARS-CoV-2; histomorphology; maternal death; neonatal outcomes; placenta; pregnancy.