The Effects of Asymptomatic Coronavirus Disease-2019 on Placenta at Third Trimester Pregnancy: A Comprehensive Study

Objective: By the time coronavirus disease-2019 (COVID-19) had been announced as pandemic, the disease was shown to have a great risk among pregnant woman if lower respiratory system is involved. We aimed to describe clinical characteristics of deliveries with asymptomatic COVID-19 infection, investigate transplacental transmission, and compare first-line histopathological findings with healthy controls. Material and Methods: We conducted a prospective cohort study of consecutive term deliveries at our tertiary hospital's obstetric unit between March and November 2021. Forty-five patients with asymptomatic reverse transcription-polymerase chain reaction (RT-PCR) positivity were matched with 45 controls with negative RT-PCR testing. All newborns of mothers with positive RT-PCR results for COVID-19 underwent a nasopharyngeal swab following delivery, and Apgar scores of the newborns were extracted from pediatric charts. Placentas were transported and fixated in 10% formaldehyde solution before pathological evaluation. Results: There were no significant differences in Apgar scores, birth weights, head circumferences, birth height, and genders between the 2 groups. RT-PCR results were negative in all of the newborns, indicating no vertical transmission. Placental focal and global calcification, and choriamnionitis frequencies were similar between the groups, whereas placental fibrin deposits were significantly more frequent in the placentas of infected pregnancies. Conclusion: There was no evidence of vertical transmission and any characteristic feature in the placentas of pregnancies with asymptomatic COVID-19 infection. Although no significant clinical implication was found, increased perivillous fibrin deposition in the study group could be a baseline step for the progression of perinatal infection.