New research indicates that the coronavirus can invade and destroy the placenta, leading to fetal death in infected women.
It’s a rare outcome in any pregnancy, but women with COVID-19 are at higher risk. Authorities believe that vaccination can help prevent these cases.
Researchers from 12 countries, including the United States, analyzed placental and autopsy tissue from 64 stillbirths and four newborns who died shortly after delivery. In all cases, they were unvaccinated women who had had COVID-19 during their pregnancy.
The study strengthens evidence from case reports and confirms that damage to the placenta, rather than infection of the fetus, is the likely cause of many stillbirths related to COVID-19, said Dr. Jeffery Goldstein, a pathologist at the School of Feinberg Medicine of Northwestern University, who was not involved in the study.
The report was published Thursday in the scientific journal Archives of Pathology & Laboratory Medicine.
Previous evidence indicates that the odds of stillbirth are higher than usual in pregnant women with COVID-19, especially the delta variant.
Vaccination recommendations include pregnant women and note that they are at higher risk of complications when infected.
The study’s lead author, Dr. David Schwartz, an Atlanta pathologist, said there are other infections that can infiltrate the placenta and cause stillbirth, usually by infecting and damaging the fetus.
A recent example is the Zika virus.
He and his colleagues wanted to see if that was the case for stillbirths in women with COVID-19. But what they found was almost the opposite: it was the placenta that was infected and largely destroyed.
“Many of these cases had more than 90% of the placenta destroyed, which is very scary,” Schwartz said.
Normal placental tissue has a healthy, fluffy reddish hue. The specimens they studied were stiff, with dark discolorations of dead tissue. Although other infections can occasionally damage the placenta, Schwartz said he had never seen them cause such consistent and extensive destruction.
The placenta is an organ that forms and attaches to the uterus during pregnancy. It connects to the umbilical cord, providing oxygen and nourishment from the mother’s bloodstream.
The virus likely reached the placenta through the bloodstream, attaching itself to susceptible cells and causing protein deposits and an unusual form of inflammation that blocked blood flow and oxygen. This, in turn, led to the death of placental tissue and suffocation, according to the researchers.
The coronavirus was also detected in some of the fetuses, but tests of asphyxia in the womb point to damage to the placenta as the most likely cause of death, they said.
A November report from the US Centers for Disease Control and Prevention found that among pregnant Americans infected with COVID-19, about one in 80 births was a stillbirth, meaning the loss of a fetus. any time after 20 weeks of gestation. Among uninfected women, the rate was 1 in 155.
Fetal deaths in the study occurred at an average of 30 weeks. A normal pregnancy lasts about 40 weeks.
It is not clear whether the omicron variant of the coronavirus also increases the risk of stillbirth. The study was conducted before this variant emerged.