Background:

Respiratory and immune changes during pregnancy can lead to viral infections. In coronavirus disease 2019 (COVID-19), clinical characteristics and perinatal risks are difficult to assess and are relatively unknown.

Objective:

To review placental pathology in asymptomatic women with COVID-19, and to evaluate effects on perinatal outcomes.

Material and method:

Retrospective, observational, cross-sectional study that included 29 pregnant women in 2020. The women underwent COVID-19 tests and were divided in two groups: 1) control, COVID-19-negative patients, and 2) asymptomatic COVID-19-positive patients; the placentas were studied at the pathology department, and clinical data were retrieved from the electronic medical record; in addition, a literature review was carried out.

Results:

When the groups were compared, no differences were observed in general data and clinical characteristics. On the day of delivery, patients 2, 4, 5, 6, 8 and 9 of the COVID-19 group were between day 0 and 10.5 after having tested positive; only patients 1, 3 and 7 had overcome the infection. There was a decrease in weeks of gestation in the COVID-19 group (37.8 ± 1.8 vs. 39 ± 0.8; p ≤ 0.05). COVID-19-positive patients' placental histopathology showed a higher prevalence of thrombotic alterations in placental villi (55.5 vs. 0 %).

Conclusions:

COVID-19 asymptomatic infection potentiates preexisting prothrombotic profile, thus increasing the risk of placental thrombosis and, potentially, of thrombosis in pregnant women.