2023 ABSTRACT: COVID-19 INFECTION in PREGNANCY - WHO IS MOST at RISK of ADVERSE OUTCOMES?

ABSTRACT

Background: COVID-19 infection during pregnancy is associated with increased rates of adverse perinatal outcomes. The mechanism by which this occurs is not understood. We have previously reported increased rates of placental histopathological lesions in these pregnancies. Aim(s) We hypothesise that, 1. trimester of infection, and 2. vaccination status, affects placental histopathology and neonatal outcomes. Method(s) Pregnant women infected with COVID-19 between January 2020 and May 2022 were retrospectively identified from Monash Health records. Maternal and neonatal data were collected alongside placental histopathological changes as categorised by the Amsterdam Criteria. Result(s) 942/21838 women had COVID-19 infection during pregnancy. Placental histopathology was available in 638 cases. Analysis of infection by trimester revealed that earlier infection was associated with increased preterm birth rate (13.5% vs. 10.3% vs. 4.5%, P = 0.0012), reduced birth weight (3108 vs. 3216 vs. 3345 g, P = 0.0061) and increased fetal loss rate (2.7% vs. 1.8% vs. 0%, P = 0.0023, in T1 vs. T2 vs. T3, respectively) (Table 1). Placental weight increased with trimester of infection (416 vs. 469 vs. 487 g, P = 0.0267). There were no differences in histopathological lesions. 300 patients were unvaccinated (>=1 dose) versus 642 double vaccinated (>=2 doses) against COVID-19 (Table 2). Double vaccination resulted in fewer placental histopathological lesions (59.0% vs. 69.9%, P = 0.0089), particularly maternal vascular malperfusion lesions (20.7% vs. 28.2%, P = 0.0127) but no difference in perinatal outcomes. Conclusion(s) COVID-19 infection earlier in pregnancy is associated with poorer perinatal outcomes. Vaccination reduced the rate of placental lesions but did not change adverse neonatal outcomes.