Blood tests may indicate a higher risk of pregnancy in patients with COVID-19
Blood tests may indicate a higher risk of pregnancy in patients with COVID-19

Blood tests may indicate a higher risk of pregnancy in patients with COVID-19

A small preliminary study from Northwestern Medicine has shown that a blood test can identify the risk of stillbirth and placentitis in pregnant women who have had COVID-19. The finding is based on another study with similar results and may have implications for how physicians screen for and address high-risk pregnancies.

Research has shown that pregnant women with COVID-19 have a higher risk of stillbirths and other pregnancy complications. Anecdotal reports have also reported potentially higher incidence of stillbirths caused by certain variants, leading to increased concern in the scientific community. Researchers identified a link between COVID placentitis, in which the virus infects the placenta, and these poor results, but can only diagnose cases of placentitis after birth by examining the placenta.

The new paper, published this week in the journal PLACENTA, highlights a link between placentitis and circulating SARS-CoV-2 virus.

“Right now we do not know if there is placental inflammation until after the fact,” said Northwestern’s Dr. Leena Mithal, the newspaper’s first author. “We are laying the groundwork for further research so that people who are diagnosed with COVID during pregnancy may in the future receive a test that will help identify pregnancies that may have a higher risk of stillbirth or fetal distress.”

Mithal is an assistant professor of pediatric infectious diseases at Northwestern University Feinberg School of Medicine and attending physician at Ann & Robert H. Lurie Children’s Hospital in Chicago. Dr. Jeffery Goldsteindirector of perinatal pathology at Feinberg, led the study and is the corresponding author.

Placentitis affects between 1% and 2% of pregnant women infected with COVID-19. Unlike many pregnancy complications, the risk of placentitis and stillbirth is not associated with the severity of the virus. Dr. Elisheva Shanesa co-investigator of the study and assistant professor of perinatal and autopsy pathology at Feinberg, said it makes it nearly impossible to predict which placentas are at risk because an asymptomatic infection can just as easily have complications as a very sick person.

Using a biostore of blood taken from pregnant women during the 2020 pandemic, the researchers looked at the blood of participants who had tested positive for COVID-19 during pregnancy – six who were positive for placentitis and 12 controls who were not. Subsequently, researchers at the Center for Pathogen Genomics and Microbial Evolution searched for RNA from the virus in the mother’s blood using the same PCR-based test normally performed on nasal swabs.

Of those who had placentitis, two had low levels of viral RNA (called viremia) in their blood; none of the checks did. One of the persons with viremia had a stillbirth, and the other had a good infant; all participants who tested negative for the marker gave birth to healthy babies.

“The part of the placenta that is infected with the virus is also the part that is in contact with the mother’s blood,” Shanes said. “So if there is infection in these cells, the virus can also be found in the blood. If a pregnant person had COVID and no placentitis, we would not expect to find viruses in the blood.”

Most pregnant patients with COVID-19 will continue to have normal pregnancies. Improved versions of this test and further studies to validate the result could help obstetricians develop plans for those at high risk for placentitis and stillbirth, Shanes said. Investigators plan to conduct follow-up studies with larger pools of participants and hope that other laboratories will build on the small amount of literature to further validate the results.

The best way to protect both parents and baby is to get vaccinated, the authors said. In their observations, stillbirths have been more common in unvaccinated patients.

“We do not know why viremia affects or does not affect some people, but the vaccine appears to protect against serious complications,” Mithal said.

The all-northwest team also includes Sebastian Otero, Lacy Simons, Judd Hultquist, Emily Miller and Egon Ozer.

The study, “Low-level SARS-CoV-2 viremia coincident with COVID placentitis and stillbirth,” received support from Friends of Prentice, the Stanley Manne Children’s Research Institute, and from institutional resources supported by the National Center for Advancing Translational Sciences (UL1TR001422). The team is also supported by the National Institute of Biomedical Imaging and Bioengineering (K08EB030120), the National Institute of Allergy and Infectious Diseases (K23AI139337) and the National Institute of Health (R21 AI163912, U19 AI135964).

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