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Covid-19 infection in pregnant people may be associated with abnormal blood flow between mothers and their babies in utero, according to new research. The findings suggest a new complication of infection by severe respiratory disease, which could help to inform monitoring and treatment methods during the pandemic.
The placenta is the first organ to form as the fetus develops and takes oxygen and nutrients from the mother's bloodstream and helps to facilitate the exchange of waste, acting “like a ventilator” for the fetus. According to the findings, the placentas of pregnant people infected with SARS-CoV-2 appear to not work as well when compared to those who are uninfected.
To come to their findings, experts at Northwestern Medicine completed pathological exams of the placentas from 16 women who tested positive for Covid-19 and delivered between March 18 and May 5, 15 of whom delivered live infants in the third trimester and one asymptomatic patient who had miscarried in the second trimester. Though the babies were largely born healthy at full-term, an analysis of the placenta showed that the placentas were “smaller than they should have been,” according to the study published in the American Journal of Clinical Pathology.
“Most of these babies were delivered full-term after otherwise normal pregnancies, so you wouldn’t expect to find anything wrong with the placentas, but this virus appears to be inducing some injury in the placenta,” said senior author Dr. Jeffrey Goldstein, assistant professor of pathology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine pathologist, in a statement.
“It doesn’t appear to be inducing negative outcomes in live-born infants, based on our limited data, but it does validate the idea that women with COVID should be monitored more closely.”
Specifically, the placentas in study participants saw two common abnormalities; the first being insufficient blood flow from mother to fetus in what is known as maternal vascular malperfusion (MVM) – a condition where the blood vessels were abnormal. Blood clots, in the placenta, or intervillious thrombi, was also observed despite its more common coaction with preeclampsia and hypertension. Neither the infants nor the placentas tested positive for the virus
The study authors do warn of several limitations, including that placentas are only submitted for examination if there is an indication of disease or other complications, which could bias the results. Furthermore, researchers grouped together symptomatic, asymptomatic, and recovered patients, which could have skewed the results. Though it is a small study, the researchers say that the findings are worrisome.
“I don’t want to draw sweeping conclusions from a small study, but this preliminary glimpse into how Covid-19 might cause changes in the placenta carries some pretty significant implications for the health of a pregnancy. We must discuss whether we should change how we monitor pregnant women right now,” said study co-author Emily Miller, assistant professor of obstetrics and gynecology at Feinberg and a Northwestern Medicine obstetrician.
Even so, the findings could help inform how pregnant women are monitored during pregnancy in the midst of the ongoing pandemic and focus efforts on tests to determine whether the placenta is functioning and if the baby is growing at a healthy rate.