SARS-CoV-2 infection in late pregnancy can lead to severe inflammatory reactions in the placenta

SARS-CoV-2 infections of women in late pregnancy often spread to their placentas and led to inflammation, according to a study by researchers at Weill Cornell Medicine and NewYork-Presbyterian. The findings suggest that further research is needed into the effects of the virus during pregnancy and underscore the current recommendation from the U.S. Centers for Disease Control and Prevention that pregnant women continue to take precautions, such as masking, social distancing and vaccination, to reduce their risk of getting pregnant. SARS-CoV-2 infection.

In the study, published April 11 in iScience, the researchers found signs of SARS-Cov-2 infection, inflammation and tissue damage in 22 of the placentas of 52 mothers who tested positive for the virus at the time of delivery in NewYork. -Presbyterian/Weill Cornell Medical Center. The researchers also found in lab studies that more recent SARS-CoV-2 variants, including the Delta variant, were more likely to infect placental tissue than the original strain.

The main message from these findings is that placental infection can occur with SARS-CoV-2 and lead to severe inflammatory responses in the placenta – raising questions about its short- and long-term effects on newborns.”

dr. Heidi Stuhlmann, co-senior author, professor and acting chair of cell and developmental biology and of biochemistry and the Harvey Klein Professor of Biomedical Sciences at Weill Cornell Medicine

The study was a collaboration that also included the labs of Dr. Robert Schwartz, associate professor of medicine in the Division of Gastroenterology and Hepatology, and Dr. Shuibing Chen, the Kilts Family Professor of Surgery, at Weill Cornell Medicine. The co-first authors are Lissenya Argueta, a senior graduate student in the Stuhlmann lab, Dr. Lauretta Lacko, a postdoctoral associate in surgery in the Chen lab, and Dr. Yaron Bram, a research associate in medicine in the Schwartz lab.

Some viral infections during pregnancy are known to increase the risk of adverse birth outcomes and developmental disabilities. Placental inflammation due to infection is seen as a possible mediator of these effects.

Although studies show that pregnant people with covid are at greater risk of certain pregnancy complications, much is still unclear about the effects of SARS-CoV-2 during pregnancy. Recent large studies indicate that SARS-CoV-2 infected mothers with moderate or severe symptoms are more likely to experience adverse events during pregnancy and after birth, for example, premature births, postpartum hemorrhage, and an increased risk of stillbirth or early neonatal death. In addition, transmission of the virus from infected mothers to their newborns appears to be extremely rare.

To shed light on these issues, the team studied the placenta — the organ that develops between the fetus and the mother to supply nutrients, oxygen and hormones to the developing fetus — of a series of 52 pregnant women who tested positive for SARS-CoV-2 at the time they delivered.

The researchers found that significant placental abnormalities were absent in four control placentas from uninfected mothers, but were present in the majority of placentas from infected mothers – 33 of 52 (64 percent) had potentially severe placental pathologies known to be present. stand as fetal vascular malperfusion or maternal vascular malperfusion, which affects maternal blood flow to the fetus, or both.

In addition, although no newborn tested positive, 22 of 52 placentas (42 percent) tested positive for SARS-CoV-2 genetic material. Two of these placentas had very high levels of the Alpha variant virus: one was associated with stillbirth, the other with severe preterm birth requiring extensive intensive care.

The researchers’ examination of the two most infected placentas revealed significant infiltration of maternal immune cells and signs of inflammatory damage to placental tissue – which likely contributed to the unfavorable birth outcomes.

Finally, the researchers showed in laboratory experiments that placental cells that come into contact with maternal blood can be infected with SARS-CoV-2. They also showed that more recent variants of the virus, including the Delta variant — the study concluded just before the Omicron wave — were generally better able to infect placental tissue, compared to the original virus.

The researchers followed further studies, including placentas infected during the Omicron wave.

“The evidence we’ve collected so far supports the idea that newer variants are better not only at infecting mothers, but also at infecting placentas,” said Dr. chen.

The team hopes to conduct long-term studies of health outcomes in children born to SARS-CoV-2 infected mothers.

“To resolve the issue of the long-term effects, we need to set up large cohort studies in which children of mothers with SARS-CoV-2 are followed for years,” said Dr. Schwartz, who is also a hepatologist at New York-Presbyterian/Weill Cornell Medical Center.