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Since the beginning of the pandemic, the question of whether newborns can become infected with the coronavirus in utero has remained open. The rare case of newborns’ testing positive for the virus has cropped up here and there, but none has presented evidence that could rule out the possibility that the illness had been transmitted once the baby was born. A new case adds another wrinkle to these studies, presenting strong evidence that the coronavirus can be transmitted directly from a pregnant woman to a fetus.

The New York Times reports that new research published in the Nature Communications journal on Tuesday suggests a COVID-19-positive baby born in a Paris hospital in March contracted the virus through the placenta of their mother, who also carried the virus. According to Dr. Daniele De Luca — the chief of the division of pediatrics and neonatal critical care at Paris-Saclay University Hospitals and lead researcher of the team that reported the case — the baby exhibited the symptom of brain inflammation but was able to recover without treatment. Now, more than three months later, the baby is “very much improved, almost clinically normal,” De Luca said, and the 23-year-old mother is healthy too.

Researchers tested the baby’s blood, placenta, amniotic-fluid cord blood, and the mother’s blood in the course of their study. De Luca said the tests indicate “the virus reaches the placenta and replicates there,” then it can infect the fetus itself, leading to “symptoms similar to adult COVID-19 patients.”

Dr. Yoel Sadovsky, who works at the University of Pittsburgh as the director of the Magee-Womens Research Institute and is not affiliated with the study, told the Times that while he finds this latest research “fairly convincing,” it still appears that coronavirus transmission in utero is exceedingly uncommon, unlike other viruses like Zika and rubella. De Luca said his team will continue to study other suspected cases of placental transmission.