How the Placenta Shields the Fetus From COVID-19

The placenta was designed by nature to keep baby both nourished and safe. Now, research reveals how it protects the developing fetus from a new foe: The virus that causes COVID-19.

“The placenta is one of the few ‘success stories’ of the pandemic,” said study co-author Dr. Elizabeth Taglauer, an assistant professor of pediatrics at Boston University School of Medicine. “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.”

To learn why rates of transmission from mother to baby during pregnancy have been very low, she and her colleagues analyzed placentas from two groups of women who delivered at Boston Medical Center between July 2020 and April 2021.

One group had normal pregnancies with no report of SARS-CoV-2 infection. The others had active COVID-19 disease during pregnancy.

The researchers examined their placentas under the microscope and used genetic and protein analysis to compare placental expression of ACE-2, an enzyme that allows SARS-CoV-2 to enter cells.

The investigators found lower levels of ACE-2 in the placentas of women with COVID-19 during pregnancy.

“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,” Taglauer said in a university news release.

The findings were recently published online in the American Journal of Pathology. They extend beyond learning more about COVID-19 during pregnancy, the study authors said.

Since the placenta has many similarities with the lung, the findings show the importance of studying the placenta to help understand a variety of lung diseases. The researchers said they also highlight the need to control ACE-2 as a way to prevent SARS-CoV-2 infections.

More information

The U.S. Centers for Disease Control and Prevention has more on COVID-19 and pregnancy.

SOURCE: Boston University School of Medicine, news release, Jan. 31, 2022