Impact of SARS-CoV-2 Omicron infection on late pregnancy: an analysis of clinical characteristics, pathology of placenta and outcomes in a case-control study.

Objectives: This study analyzes clinical features and placental pathology of pregnant women infected with SARS-CoV-2 Omicron variants and conducts a two-year follow-up to assess childbirth risks and newborn health outcomes. Methods: Retrospective analysis of 46 Omicron-infected pregnant women (Omicron group) and 96 uninfected pregnant women (Control group). Results: Omicron group exhibited higher risk of fetal distress rate, lower leukocyte and lymphocyte counts, and higher C-reactive protein levels compared to the control group. Most infected women (93.48 %) were symptomatic, with fever being the most common symptom. Histologically, acute maternal and fetal inflammatory response were observed in 28.26 and 8.70 % of the Omicron group, but no significant difference from the control group. Maternal vascular malperfusion (50.00 %) and fetal vascular malperfusion (4.34 %) were present in the Omicron group at rates comparable to the controls. Among the 39.13 % of newborns tested for SARS-CoV-2 within three days of birth, 33.33 % tseted positive. Of these positive neonates, 83.33 % were symptomatic, universally presenting with fever, and one developed pneumonia. Conclusions: Placental pathological findings were non-specific to the Omicron variant. Notably, the two-year follow-up indicated that neither the Omicron-infected mothers nor their newborns experienced long-term adverse health outcomes.