COVID-19 Virus Clears from Placenta Weeks after Recovery: JAMA
USA: Researchers have found in a small case-control study that the virus causing COVID-19 does not persist in placental tissue after a pregnant patient recovers from acute infection. These findings suggest that ongoing placental infection is unlikely in the weeks to months following illness, even in pregnancies with adverse outcomes. The study has been published in the journal JAMA Network Open.
The research letter, led by Shelli F. Farhadian from Yale School of Medicine, examined whether SARS-CoV-2 components remain in placental tissue after maternal recovery. Infection during pregnancy has previously been associated with placental inflammation and, in severe cases, fetal loss. However, it has remained unclear whether the virus continues to reside in the placenta after the acute phase of illness has resolved.
For this purpose, the investigators conducted a case-control analysis of placental samples collected at delivery between October 2020 and December 2024. The study included three groups: placentas from pregnancies before the COVID-19 pandemic, those with confirmed acute COVID-19 placentitis, and cases where mothers had recovered from SARS-CoV-2 infection. Advanced laboratory techniques, including immunohistochemistry and RNA in situ hybridization, were used to detect viral proteins and genetic material within placental tissues.
A total of 12 placental samples were analyzed.
Key Findings:
- In acute infection cases, SARS-CoV-2 proteins and RNA were clearly detected within placental cells.
- These placentas showed characteristic pathological features such as inflammation, fibrin deposition, and tissue injury.
- Placentas from women who had recovered from COVID-19 (40 to 212 days after infection) showed no detectable viral protein or RNA.
- This absence of viral material was consistent across all seven recovered cases.
- The recovered group included both stillbirths and healthy full-term deliveries.
- Even when inflammatory changes were present, there was no molecular evidence of persistent viral infection in the placenta.
The findings indicate that while SARS-CoV-2 can directly affect placental tissue during acute infection, it does not appear to remain in the placenta once the mother has recovered. This distinction is important, as lingering placental abnormalities observed after infection may be driven by immune or vascular responses rather than ongoing viral activity.
The authors also noted that detection of viral material in other tissues after infection does not necessarily imply active replication. In this study, the absence of both viral protein and RNA in placental tissue strengthens the conclusion that persistent infection is unlikely in the post-recovery phase.
However, the study has limitations, including its small sample size and retrospective design, which may limit the ability to generalize findings across different populations or viral variants. Despite these constraints, the research provides valuable molecular evidence supporting the absence of SARS-CoV-2 persistence in placental tissue after maternal recovery.
Overall, the study offers reassurance regarding placental health following COVID-19 and highlights the need for further research to better understand the mechanisms underlying post-infection placental changes.
Reference:
Farhadian SF, Orlinick B, Milano KM, Mekael D, Kliman HJ. Absence of SARS-CoV-2 in Placental Tissue After Maternal COVID-19. JAMA Netw Open. 2026;9(4):e268567. doi:10.1001/jamanetworkopen.2026.8567
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