New Research Defines Intrauterine Placental Transmission of COVID-19 From Pregnant Women to the Fetus

Reports of increasing numbers of pregnant women with COVID-19 show that most neonates (newborn infants) are uninfected by the new coronavirus, SARS-CoV-2. However, a very small number of neonates have tested positive for COVID-19. This has led investigators to examine whether mother-to-infant (vertical) transmission occurs and, if it does, whether it develops in the uterus prior to delivery, and how it happens in a new research article published in the Archives of Pathology & Laboratory Medicine (ARCHIVES).

“Evaluating placentas from neonates with COVID-19 is instrumental in determining the potential role and significance of transplacental transmission of the coronavirus,” said David A. Schwartz, MD, FCAP, a specialist in placental pathology and medical epidemiology as well as global maternal health and the lead author of the study. According to Dr. Schwartz, results from recent studies suggest that in rare instances, transplacental transmission of the coronavirus is occurring.

In their research, Dr. Schwartz and his co-authors provide guidance and photographic illustrations demonstrating criteria for the diagnosis of intrauterine placental infection and fetal transmission with coronavirus occurring before birth. In order to determine the occurrence of prenatal transplacental infection, the authors recommend that health care professionals involved with obstetric care consider saving and testing select placentas using either antibody staining (immunohistochemistry) for SARS-CoV-2, or that identification of the viral nucleic acid be performed using in situ RNA hybridization or RNAscope methods. The study authors believe that positive staining of fetal cells using either of these techniques in placentas from neonates testing positive for COVID-19 is indicative of transplacental transmission of the infection. They also provide clinical criteria for diagnosis of early neonatal COVID-19 infections.

This new research—an international collaboration by Drs. Schwartz, Babak Beigi, Fereshteh Moshfegh, Nazanin Zafaranloo, Luisa Patanè, and Denise Morotti—expands the body of science available on the transmission of SARS-CoV-2 between mother, the placenta and infant, and recognizes a recent Italian study that demonstrates the virus pathologically in specific fetal cells of the placenta (trophoblast) from two infected newborn infants, indicating infection of fetal tissues before delivery. The largest of fetal organs, the placenta has been important for understanding mechanisms of transmission of several different viruses from pregnant women to the fetus including HIV, Ebola and Zika viruses (the latter virus was previously identified in the placenta from an infected fetus with the congenital Zika syndrome by Dr. Schwartz).

“Identification of the virus in fetal cells of the placenta provides strong evidence of intrauterine fetal infection. Even though the relative risks and proportions of neonatal infection remain unknown, identifying the mechanisms of viral transmission can help guide management of pregnant women with COVID-19 and neonates,” said Dr. Schwartz. “From a clinical perspective, identifying viral transmission mechanisms can help in making decisions regarding need for cesarean sections, isolation of neonates, breast feeding and other factors.”

Pathologists are medical doctors who are critical members of the health care team, combining a scientist’s understanding of what laboratory evidence suggests and a specialty physician’s knowledge of medicine to determine the correct diagnosis. As the international health emergency continues to evolve, the public should follow the Centers for Disease Control and Prevention’s (CDC) recommendations for prevention and treatment of the COVID-19 disease.

About ARCHIVES

Published since 1926, Archives of Pathology & Laboratory Medicine (ARCHIVES) is the monthly international peer-reviewed journal of the College of American Pathologists. It was voted in 2009 the only pathology journal among the top 100 most influential journals of the past 100 years by the BioMedical and Life Sciences Division of the Special Libraries Association.

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 serves patients, pathologists, and the public by fostering and advocating excellence in the practice in the practice of pathology and laboratory medicine worldwide. For more information, read the CAP Annual Report at CAP.ORG.

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