Though rare, Covid during pregnancy can increase a woman’s risk of stillbirth.

Research published Thursday paints a startling picture of the destructive toll Covid-19 can take on pregnant women and their growing fetuses.

The virus can attack and destroy the placenta, a vascular organ that serves as a fetus’s lifeline, leading to asphyxiation and stillbirth, according to the study in the journal Archives of Pathology & Laboratory Medicine.

“We have never seen this level of destruction from an infectious illness before. It rendered the placenta unfit to carry out its duties,” said Dr. David Schwartz, a perinatal pathologist in private practice in Atlanta, who led the study. “These fetuses and newborns died from asphyxiation due to lack of oxygen.”

“It’s almost the exact opposite of what we see in other infectious diseases like zika, rubella or syphilis,” he said. “It’s not the fetus that is being attacked and destroyed by the virus. It’s the placenta.”

In the study, Schwartz and his team examined 68 perinatal deaths in 12 countries. All 68 babies were either stillborn or died within seven days of being born. All had mothers who were unvaccinated and had been infected with the coronavirus while pregnant. Their study included examinations of all 68 placentas as well as 30 autopsies.

While no fetal abnormalities aside from asphyxiation stuck out, the placentas showed a trend, which the researchers are calling “SARS-CoV-2 placentitis.”

It consists of three factors: A build up of a protein called fibrin, which causes clotting in the organ’s delicate vascular system; the death of cells in the protective cell layer of the placenta; and unusual inflammation in the placenta.

On average, more than three-quarters of the placenta was so severely damaged, the organ couldn’t deliver oxygen and nutrients to the growing baby. In some cases, more than 90 percent of the placenta was dead.

Fibrin deposition can occur in completely normal, uncomplicated pregnancies, said Dr. Kjersti Aagaard, a professor of maternal-fetal medicine at Baylor College of Medicine and Texas Children’s Hospital who was not involved in the new study. “But what you don’t see is three-quarters of the placenta filled with these. No fetus can survive that.”

Mild Covid can still cause damage

Pregnant people are naturally more susceptible to infection because pregnancy weakens the immune system to keep a person’s body from attacking the fetus. What makes Covid infection different from other viral infections during pregnancy is how it infects the body and, in particular, how that infection lingers and restricts blood flow to the placenta.

“It causes this severe reaction deeper in the respiratory tree. Recovery has been slow and patients have had this continuous damage to their lungs they can’t recover from,” said Dr. Ellie Ragsdale, director of fetal intervention at University Hospitals Cleveland Medical Center, who was not involved with the new study.

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But Covid can cause serious problems even in women without severe disease, Ragsdale said. “The thing that is the scariest about this is we are seeing this in women who have very mild symptoms from Covid. This damage to the placenta may be their only symptom.”

If only a small portion of the placenta is damaged, it may not cause any complications at all.

But if it’s a larger area, Ragsdale said, “the first thing you’ll see is growth restriction from the baby and decreased fetal movement. The final thing that you see is a pregnancy loss, and sometimes that progression happens very quickly.”

According to Schwartz, early research suggests SARS-CoV-2 placentitis happens over a period of days up to two weeks. Obstetricians are now being advised to perform third-trimester ultrasounds on women who have been infected with Covid during pregnancy to screen for warning signs that could endanger the baby.

“Obstetricians see placental insufficiencies happening in their practice all the time. You can never reverse it but you can contemplate delivery. If it’s medically feasible, you get the fetus out of there,” Schwartz said.

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Aagaard stressed that stillbirth due to Covid is rare, but the infection does raise a woman’s risk.

A Centers for Disease Control and Prevention study published in November found that stillbirths among mothers in the U.S. who had tested positive for Covid while pregnant increased nearly three-fold during the delta wave that started last July.

Around 0.59 percent of pregnancies resulted in stillbirths pre-pandemic. In the first part of the pandemic, 0.98 percent of pregnancies in expectant mothers infected with the coronavirus resulted in stillbirths. Once the delta variant took hold, the rate jumped to 2.7 percent of Covid-infected expectant mothers.

The importance of vaccination

Doctors say the “single best” way for pregnant women to protect themselves and their babies is to get the Covid vaccine.

“While there are a lot of things we don’t know how to prevent in pregnancy, including stillbirths unrelated to Covid-19, we can prevent Covid-19-related stillbirths with a vaccine,” Aagaard said.

The CDC, the American College of Obstetricians & Gynecologists, and the Society for Maternal-Fetal Medicine all strongly recommend that pregnant women be vaccinated against Covid.

Evidence demonstrating the safety of the vaccines to pregnant women and their babies continues to build. An Israeli study, published Thursday in JAMA Pediatrics, included more than 24,000 babies, and found no difference in the risk of preterm birth or low birth weight among mothers who were vaccinated or unvaccinated. In other words, the vaccine didn’t increase the risk of these outcomes in pregnant women. There were also no significant differences in the number of babies who were hospitalized in the first five months of life.

“These two studies side by side reinforce the notion that the single best decision that any pregnant person and their family can make at this moment in time is to get the Covid vaccine,” Aagaard said. “That is the best thing they can choose to do to improve the chance that they are going to have a healthy uncomplicated delivery.”

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