Q&A: Even asymptomatic COVID-19 may increase pregnancy risks, study finds

Regardless of disease severity, COVID-19 elicited immune responses in pregnant women, which in turn caused inflammation in the placenta, according to data published in Cell Reports.

The findings reinforce the importance of vaccination during pregnancy, researchers said.

“Prior to this study, this response was only thought to occur in severe COVID-19 cases,” study author Ilhem Messaoudi, PhD, professor and chair of the department of microbiology, immunology and molecular genetics at University of Kentucky, said in a press release. “We now know that even a mild infection that doesn’t even register with a patient is still being registered by the maternal immune system. The placenta had very clear signs of having sensed that there was an infection.”

Healio spoke with Messaoudi to learn more about the immune response to SARS-CoV-2 infection during pregnancy and its effect on outcomes.

Healio: What prompted your research on this topic?

Messaoudi: A healthy pregnancy relies on tightly orchestrated immune adaptations to ensure fetal tolerance and growth while preserving antimicrobial responses — dubbed “the immunological clock of pregnancy”. Deviations from these precise changes can lead to adverse outcomes for both mother and fetus. Maternal infection can derail these immune adaptations even if the pathogen does not infect the placenta. In this study, we wanted to understand how a respiratory infection can impact the maternal-fetal interface and the consequences associated with such an infection.

Healio: What is the take home message?

Messaoudi: Asymptomatic and mild SARS-CoV-2 infection results in significant inflammation in both maternal blood and the maternal-fetal interface, [as well as] the activation of pathways associated with antiviral immune responses despite the lack of virus in placental tissue.

Healio: Were any of your findings surprising?

Messaoudi: We were surprised by the magnitude of the inflammatory responses we detected given that none of the subjects enrolled in this study experienced severe COVID-19. In fact, half of the subjects tested positive upon admission to labor and delivery and were unaware that they were infected. These data highlight the strong connection between the circulating immune cells and those that reside at the maternal-fetal interface.

Healio: What is the clinical significance of the findings?

Messaoudi: Heightened inflammation at the maternal-fetal interface can have dramatic consequences for the offspring. Indeed, recent studies indicate that babies born to mothers who were infected with SARS-CoV-2 during pregnancy were at increased risk of preterm birth, circulatory problems and infection.

Healio: What research would you like to see next?

Messaoudi: We would like to carry out an in-depth analysis of the neonatal immune system of babies born to mothers who were infected with SARS-CoV-2 during pregnancy. These data have also prompted [us] to investigate the impact of other maternal factors on the immune landscape of the maternal-fetal interface.

Healio: Is there anything else you would like to highlight about this study?

Messaoudi: The findings in this study highlight the importance of getting vaccinated against COVID-19 during pregnancy to protect both mother and developing fetus against consequences of SARS-CoV-2 infection.

References:

• Sureshchandra S, et al. Cell Rep. 2022;doi:10.1016/j.celrep.2022.110938.
• University of Kentucky study: Asymptomatic COVID-19 could still cause pregnancy risks. https://www.eurekalert.org/news-releases/954436. Published May 31, 2022. Accessed June 7, 2022.