• The case was published in Nature Communications journal on Tuesday.
  • The authors said the baby's brain bore evidence of inflammation caused by the coronavirus. They also said they found sufficient evidence that it had crossed into the baby via the placenta.
  • Several prior studies indicated that placental or cervical transmission was possible, but the case study from the Antoine Beclere hospital in Paris now serves as proof.
  • However it is very rare. The paper's lead author said "pregnant women should be reassured" because "in most cases there will be no damage to the baby."
  • Visit Business Insider's homepage for more stories .

Doctors in France have reported what they say is the first confirmed case of an unborn child contracting the coronavirus from their mother while still in the womb.

The case was the subject of a paper titled "Transplacental transmission of SARS-CoV-2 infection," which was published in the peer-reviewed journal Nature Communications on Tuesday. Details of the paper were first reported by The Guardian.

Until now, there has been some limited evidence suggesting that an unborn child could catch the coronavirus from inside the womb, but the paper's authors, from the Antoine Beclere hospital in Paris, confirmed "transplacental transmission of SARS-CoV-2" was possible.

They said that a 23-year-old woman was admitted to the hospital with a fever and cough on March 24 when she was more than 35 weeks pregnant with a boy.

TOLUCA, MEXICO - MAY 29: A doctor holds the newborn son of a patient with COVID-19 at Monica Pretelini Maternal Hospital on May 29, 2020 in Toluca, Mexico. The Government of the Estado de Mexico adapted the perinatal Hospital to treat pregnant patients tested positive of coronavirus. (Photo by Cristopher Rogel Blanquet/Getty Images)
TOLUCA, MEXICO - MAY 29: A doctor holds the newborn son of a patient with COVID-19 at Monica Pretelini Maternal Hospital on May 29, 2020 in Toluca, Mexico. The Government of the Estado de Mexico adapted the perinatal Hospital to treat pregnant patients tested positive of coronavirus. (Photo by Cristopher Rogel Blanquet/Getty Images)
Cristopher Rogel Blanquet/Getty Images

The mother tested positive for the coronavirus, gave birth via Cesarean section, and the baby was immediately taken to the natal intensive care unit of the hospital.

The baby tested positive for the virus. He later recovered and was discharged from hospital 18 days later, the doctors wrote.

The doctors said the baby's brain bore evidence of inflammation caused by the coronavirus, which had crossed the placenta into the baby's bloodstream.

They ruled out the chance that the baby caught the virus after birth via viral or bacterial means.

"The placenta showed signs of acute and chronic intervillous inflammation consistent with the severe systemic maternal inflammatory status triggered by SARS-CoV-2 infection," the authors said.

TOPSHOT - A pregnant woman wearing a face mask as a precautionary measure walks past a street mural in Hong Kong, on March 23, 2020, after the citys Chief Executive announced plans to temporarily ban the sale of alcohol in bars and restaurants as a measure to help stop the spread of the COVID-19 caused by the novel coronavirus. - Hong Kong will ban all non-residents from entering the city from midnight on March 24, 2020 in a bid to halt the coronavirus, its leader says, as she unveils plans to stop restaurants and bars serving alcohol. (Photo by ANTHONY WALLACE / AFP) (Photo by ANTHONY WALLACE/AFP via Getty Images)
TOPSHOT - A pregnant woman wearing a face mask as a precautionary measure walks past a street mural in Hong Kong, on March 23, 2020, after the citys Chief Executive announced plans to temporarily ban the sale of alcohol in bars and restaurants as a measure to help stop the spread of the COVID-19 caused by the novel coronavirus. - Hong Kong will ban all non-residents from entering the city from midnight on March 24, 2020 in a bid to halt the coronavirus, its leader says, as she unveils plans to stop restaurants and bars serving alcohol. (Photo by ANTHONY WALLACE / AFP) (Photo by ANTHONY WALLACE/AFP via Getty Images)
ANTHONY WALLACE/AFP via Getty Images

The doctors pointed out that there have been similar cases of babies being born with the coronavirus in the past, but until now, they had not been able to say definitively whether babies could contract the virus in utero.

A small study done on 31 women in Italy in March and April had found some evidence showing that unborn babies could catch the virus from their mothers.

Three other studies published in March had also found evidence that it was possible.

The doctors in France wrote: "We have demonstrated that the transplacental transmission of SARS-CoV-2 infection is possible during the last weeks of pregnancy."

"Other cases of potential perinatal transmission have recently been described, but presented several unaddressed issues," the authors said.

KAZAN, RUSSIA - JUNE 5, 2020: A pregnant patient during an ultrasound at the Perinatal Center at Tatarstan's Republican Clinical Hospital during the COVID-19 pandemic. Yegor Aleyev/TASS (Photo by Yegor Aleyev\TASS via Getty Images)
KAZAN, RUSSIA - JUNE 5, 2020: A pregnant patient during an ultrasound at the Perinatal Center at Tatarstan's Republican Clinical Hospital during the COVID-19 pandemic. Yegor Aleyev/TASS (Photo by Yegor Aleyev\TASS via Getty Images)
Yegor Aleyev\TASS via Getty Images

However, Daniele De Luca, the lead author and medical director of pediatrics at the Paris hospital, told The Guardian that cases like this are very rare.

"Pregnant women should be reassured," he said.

"Pregnancy is very controlled and if you have something like this, it can be controlled. In most cases there will be no damage to the baby."

"There are many things we can do, but we can't close our eyes and say this is never going to happen."

The long-term effect of the coronavirus on coronavirus-positive pregnant women and their unborn children remains unknown.

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