Researchers discover how placenta may block COVID-19 virus transmission to babies

Boston University researchers, looking at the very low rates of COVID-19 spread from pregnant mother to baby, have discovered how the placenta may be blocking virus transmission to babies during pregnancy.

The new study may give scientists clues about blocking COVID infections in other patients.

The research zeroes in on ACE-2, the receptor that allows SARS-CoV-2 to enter cells. The study from the Boston University School of Medicine has shown that pregnant women who were infected with COVID had lower ACE-2 levels in their placentas compared to women with normal (COVID negative) pregnancies.

“We think that when a woman has COVID-19 in pregnancy, the placenta is shedding off ACE-2 as a way to block SARS-CoV-2 from being passed to the fetus,” said co-author Elizabeth Taglauer, assistant professor of pediatrics at the Boston University School of Medicine.

The study — published in the American Journal of Pathology — involved collecting placentas from two groups of women who delivered at Boston Medical Center from July 2020 to April 2021.

The first group was women who had normal pregnancies and no report of COVID infection. The second group of women were SARS-CoV-2 positive and had active COVID disease during their pregnancies.

The researchers observed the ACE-2 expression in the women’s placentas under the microscope, and compared placental ACE-2 expression using genetic and protein analysis techniques.

The placenta has many similarities with the lung, so this study also highlights the importance of studying the placenta to help understand a variety of lung diseases, according to the scientists. The research also shows the important role of controlling ACE-2 as a way to prevent COVID infections.

“The placenta is one of the few ‘success stories’ of the pandemic,” said Taglauer, a neonatologist at Boston Medical Center. “If we understand how the placenta is naturally protecting babies from COVID-19, this may provide important information for therapies and strategies to help prevent other SARS-CoV-2 infections from continuing to spread.”

The Centers for Disease Control and Prevention encourages all pregnant people — or people who are thinking about becoming pregnant and those breastfeeding — to get vaccinated to protect themselves from COVID.