NORTHFIELD, Ill., Feb. 10, 2022 --- Unvaccinated pregnant women risk delivering stillborn babies due to placental failure caused by COVID-19 infection, which destroys the placenta and deprives the fetus of oxygen, according to research reported online in Archives of Pathology and Laboratory Medicine, the scientific journal published by the College of American Pathologists (CAP).
Atlanta-based pathologist David Schwartz, MD, MS Hyg, FCAP, a leading perinatal pathology expert, led a 44-member international research team that studied 64 stillbirth cases and four early neonatal deaths from 12 countries to determine how COVID-19 caused perinatal deaths. All the pregnant mothers were unvaccinated. Though viral variants were not identified, it is believed many infections were the Delta variant and none were Omicron.
In November, the U.S. Centers for Disease Control and Prevention reported that pregnant women with COVID-19 have increased risk for stillbirths. Although stillbirths attributable to COVID-19 are a risk, they are not common.
“Our study identified placental insufficiency as the root cause for stillbirths in women with COVID-19 during pregnancy. We found that in all cases the placentas from infected mothers had a severe abnormality known as SARS-CoV-2 placentitis,” said Schwartz. “The viral-induced lesions in the placenta obstructed maternal and fetal blood flow and oxygen exchange and caused irreparable damage and necrosis of placental tissues. Among the 68 cases, an average of 77 percent of the placenta had been destroyed and rendered useless for supporting critical fetal needs, resulting in stillbirth or early neonatal death.”
Worldwide, it is estimated there are up to six million stillbirths a year, and most result from placental failure. The placenta is the largest organ of the fetus and its sole source of oxygen. After attaching to the uterine lining, it continues to develop, serving as the life support system for the fetus until birth.
Schwartz added that the most frequent placental abnormality, observed in 100 percent of the cases, was increased fibrin (a key protein involved with blood clotting), which in almost all cases was “massive” and obstructed blood and oxygen flow to the placenta. All placentas also showed trophoblast necrosis, or death of cells that comprise the major placental cell barrier between the mother and fetus. Another placental complication caused by COVID-19 is a rare accumulation of inflammatory cells called chronic histiocystic intervillositis, which was observed in 97 percent of the cases studied by Schwartz and colleagues. Post-mortem examinations revealed that a small number of fetuses had the virus in their internal organs. Despite this finding, there were no autopsy outcomes relating to the SARS-CoV-2 that would have accounted for their deaths.
“Unlike other viral, bacterial and parasitic infections that occur in pregnancy and cause stillbirth by passing through the placenta and damaging fetal organs, SARS-CoV-2 has a very different mechanism. It causes extensive damage to the placenta and stillbirth occurs from lack of oxygen,” Schwartz explained. “The placental destruction is so severe that whether or not the fetus becomes infected might be irrelevant.”
SARS-CoV-2 reaches the placenta by traveling through the mother’s bloodstream, a process known as viremia. Schwartz said he hopes vaccination of women for COVID-19 either before or during pregnancy may reduce the risk for viremia and prevent placental infection and stillbirth.
“This new knowledge of the extent of placental damage and the mechanism of stillbirth from COVID-19 could be valuable for obstetricians and perinatologists when making clinical management decisions,” Schwartz said. “Also, new investigational medications for COVID-19 might be effective in preventing maternal viremia and subsequent placental damage.”
About the College of American Pathologists
As the world’s largest organization of board-certified pathologists and leading provider of laboratory accreditation and proficiency testing programs, the College of American Pathologists (CAP) serves patients, pathologists, and the public by fostering and advocating excellence in the practice of pathology and laboratory medicine worldwide. As a 501(c)(6) membership organization, the CAP is the only entity representing pathologists with unrestricted advocacy capability and a political action committee, PathPAC. For more information, visit yourpathologist.org to watch pathologists at work and see the stories of the patients who trust them with their care. Read the CAP Annual Report.
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