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Study: Placenta may block COVID-19 transmission to babies during pregnancy

Study: Placenta may block COVID-19 transmission to babies during pregnancy
Levels of an enzyme in the placenta may explain why pregnant people with COVID-19 rarely pass the virus to their newborns. File photo by Molly Riley/UPI | License Photo

Jan. 31 (UPI) -- The reason few pregnant women pass COVID-19 to their newborns, despite experiencing serious complications themselves, may reside in the placenta, a study published Monday by the American Journal of Pathology found.

Placentas collected from 16 pregnant people diagnosed with COVID-19 in their second or third trimesters contained lower levels of an enzyme called angiotensin-converting enzyme 2, or ACE-2, than those without the virus, the data showed.

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ACE-2 allows the virus that causes COVID-19 to enter human cells and spread throughout the body, the researchers said.

"We think that when a woman has COVID-19 in pregnancy, the placenta is shedding off ACE-2 as a way to block [the virus] from being passed to the fetus," study co-author Dr. Elizabeth S. Taglauer said in a press release.

RELATED Study confirms risks of COVID-19 in pregnancy for unvaccinated mothers, babies

"This may provide important information for therapies and strategies to help prevent other ... infections from continuing to spread," said Taglauer, an assistant professor of pediatrics at Boston University School of Medicine.

Research has indicated that pregnant people with COVID-19 are at higher risk for birth complications, including preterm delivery.

However, the risk for their passing the virus to their newborns is low, studies suggest.

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For this study, Taglauer and her colleagues collected placentas from two groups of people who delivered babies at Boston Medical Center between July 2020 and April 2021.

The first group had normal pregnancies and no confirmed COVID-19 diagnosis, while the second tested positive and had active disease during the second or third trimesters, the researchers said.

The researchers evaluated the presence of ACE-2 in placental tissue using a microscope, they said.

RELATED Study: Fetal infection with COVID-19 possible, but unlikely

Given that the placenta has many similarities with the lungs, in terms of tissue structure, the findings could help better understand how COVID-19 enters cells and identify ways to prevent infections by controlling ACE-2 levels, according to the researchers.

Understanding "how the placenta [may be] naturally protecting babies from COVID-19" could be important, Taglauer said.

"The placenta is one of the few 'success stories' of the pandemic," she said.

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