Study: COVID-19 Vaccine Does Not Damage Placenta in Pregnancy

Aislinn Antrim, Associate Editor

Researchers found no evidence of abnormal blood flow between the mother and fetus or problems with fetal blood flow following COVID-19 vaccination.

A new study has found that women who received the COVID-19 vaccine during pregnancy had no evidence of injury to the placenta, adding to the body of research demonstrating that COVID-19 vaccines are safe in pregnancy.

“We have reached a stage in vaccine distribution where we are seeing vaccine hesitancy, and this hesitancy is pronounced for pregnant people,” said co-author Emily Miller, MD, in a press release. “Our team hopes these data, albeit preliminary, can reduce concerns about the risk of the vaccine to the pregnancy.”

The study, published in Obstetrics and Gynecology, is the first to the authors’ knowledge that examines the impact of COVID-19 vaccines on the placenta. Analyzing the placenta is typically a good way to understand any issues during pregnancy, corresponding author Jeffery Goldstein, MD, PhD, said in the press release.

“The placenta is like the black box in an airplane,” Goldstein explained. “If something goes wrong with a pregnancy, we usually see changes in the placenta that can help us figure out what happened. From what we can tell, the COVID-19 vaccine does not damage the placenta.”

The investigators collected placentas from 84 vaccinated patients and 116 unvaccinated patients who delivered at Prentice Women’s Hospital in Chicago. They pathologically examined the placentas whole and microscopically following birth. Most of the vaccinated patients had received their vaccines during their third trimester and all had received either the Moderna or Pfizer COVID-19 vaccines.

The placenta is the first organ that forms during pregnancy, performing duties for most of the fetus’s organs while they’re still forming. The placenta also manages hormones and the immune system and tells the mother’s body to welcome and accept the fetus rather than rejecting it as a foreign intruder.

“The internet has amplified a concern that the vaccine might trigger an immunological response that causes the mother to reject the fetus,” Goldstein said in the press release. “But these findings lead us to believe that doesn’t happen.”

According to the press release, the team also looked for abnormal blood flow between the mother and fetus and problems with fetal blood flow. They noted that both of these issues have been seen in pregnant patients who tested positive for COVID-19. The rate of these injuries was the same in the vaccinated patients as for control patients, Goldstein said in the press release.

Finally, the team examined the placentas for chronic histiocytic intervillositis, a complication that can happen if the placenta is infected, in this case, by SARS-CoV-2. Although the researchers did not find any cases in vaccinated patients, they noted that it is a very rare condition that would require a larger sample size to differentiate between vaccinated and unvaccinated patients.

Understanding the safety of these vaccines in pregnancy is paramount, especially because the team’s earlier research in 2020 found that placentas of women who tested positive for COVID-19 while pregnant showed evidence of injury. Miller said pregnant patients who want to get vaccinated to avoid contracting COVID-19 should feel safe doing so.

“We are beginning to move to a framework of protecting fetuses through vaccination, rather than from vaccination,” Miller said in the press release.

Goldstein agreed, and noted that research has confirmed that vaccinated pregnant women make COVID-19 antibodies after vaccination and successfully transfer these antibodies to their infants.

“Until infants can get vaccinated, the only way for them to get COVID antibodies is from their mother,” Goldstein said in the press release.

REFERENCE

COVID-19 vaccine does not damage the placenta in pregnancy. News release. Northwestern University; May 11, 2021. https://news.northwestern.edu/stories/2021/05/covid-19-vaccine-does-not-damage-the-placenta/?fj=1. Accessed May 19, 2021.