Effect of asymptomatic COVID-19 infection on the placenta in the third trimester of pregnancy: A prospective case-control study.

To clarify the effect of asymptomatic coronaviruse disease-2019 (COVID-19) positivity on the placenta in the third trimester of pregnancy.

Materials and methods: This prospective, case-control study included 30 pregnant women diagnosed with asymptomatic COVID-19 between April 30, 2021 and July 20, 2021 who delivered after the 34^th gestational week, and a control group of 30 pregnant women without COVID-19, who delivered between April 2021 and July 2021, matched to the study group regarding age, gestational age and body mass index. Outcomes were compared in terms of demographic characteristics, serum blood outcomes, neonatal results, complications and placental histopathological findings.

Results: The mean age of the study population was 28.8 years and the mean gestational week was 38.2 weeks. The C-reactive protein levels (38.2 mg/L vs 5.8 mg/L, p=0.001) and ferritin levels (266.4 μg/L and 40.5 μg/L, p=0.001) were significantly higher in the COVID-19-positive pregnant women. The lymphocyte level was significantly higher in the non-COVID-19 pregnant women (p=0.040). Mural hypertrophy was determined at a significantly higher rate in COVID-positive pregnant women (83.3% vs 30.0%, p=0.001). Multivariate regression analysis showed that only COVID-19 positivity increased the presence of mural hypertrophy in pregnant women with asymptomatic COVID-19 (4.716-fold, 95% confidence interval=1.012-22.251).

Conclusion: The results of this study demonstrated that asymptomatic COVID-19 had no significant effect on pregnancy and neonatal complications. However, mural hypertrophy in the placenta was found at a significantly higher rate in pregnant women with asymptomatic COVID-19.