Maternal and perinatal outcomes and placental pathologic examination of 29 SARS-CoV-2 infected patients in the third trimester of gestation

Abstract

Aim: On December 31, 2019, an unknown outbreak of pulmonary disease was reported in China. The novel coronavirus SARS-CoV-2 was the etiologic agent of this disease, and responsible of the current pandemic of COVID-19. Accumulated evidence on placental features is based most on case-reports and small case-series, with differing results.

Methods: We gathered a cohort of 29 infected pregnant mothers who delivered 32 newborns, and had placentas available for pathologic examination. Placentas were compared with a control group.

Results: Of the 29 mothers, clinical and radiological features were similar to what was already described in COVID-19. Pregnancy modified some analytical parameters. One of the mothers succumbed to the disease. Of the 32 newborns, 1 developed an early infection, with positive reverse-transcriptase polymerase chain reaction (RT-PCR) at 48 h of life, with an initial RT-PCR negative. SARS-CoV-2 presence was assessed on placental tissue with immunohistochemistry and RT-PCR, both were negative. All newborns had good clinical outcomes. No differences in morphological placental findings were found among both groups.

Conclusion: Lack of statistically significant differences among case and control groups suggest that placentas from SARS-CoV-2 infected mothers represent a cohort of normal placentas only submitted because of maternal SARS-CoV-2 status. To the best of our knowledge, no irrefutable cases of vertical transmission have been yet described. Other authors have failed to demonstrate presence of viral RNA in placental tissue. Accumulated knowledge suggests that if vertical transmission is possible, it is a rare event.

Keywords: COVID-19; SARS-CoV-2; coronavirus; placental pathology; vertical transmission.

Figure 1

Microscopic features of placentas. (a) Normal term villi. Figure shows slender villi with a high proportion of capillary vessels forming vasculosyncytial membranes, with little intervening stroma. A thin layer of intervening syncytiotrophoblast can be seen. Although congestive, villi do not fulfill criteria for diagnosis of villous chorangiosis (H&E ×400). (b) Villous chorangiosis. Villi show an increased number of capillary cross‐sectional profiles per villus (per definition, at least 10 capillaries per villus are required to fulfill minimal criteria for villous chorangiosis) (H&E ×400). (c) Delayed villous maturation. Terminal villi show features that resemble immature intermediate villi. Villi tend to be larger, with an increased amount of stroma, which may be edematous. There is usually a thick layer of syncytiotrophoblast with scattered persistent cytotrophoblast cells. Villous capillaries are nonperipherical and do not to merge with the overlying syncytiotrophoblast, failing to form vasculosyncytial membranes. Delayed villous maturation may be seen in association with villous chorangiosis. Compare villous features with A (H&E ×400)