Babies may be able to contract coronavirus in the womb, doctors in France say.

A study reports the case of a pregnant woman with Covid-19 passing it on to her baby via the placenta.

Previous studies have suggested transmission of the virus may occur in the period immediately before and after birth.

But it is unclear whether this takes place via the placenta, a cervical route or as a result of environmental exposure.

Now researchers have reported a case that suggests transmission in the womb may be possible.

A pregnant 23-year-old was admitted to hospital in March with a fever and severe cough, and tested positive for Covid-19.

Three days later her baby was born by caesarean. Tests one hour after birth, then again three and 18 days later, showed positive results for the presence of the virus.

Further tests on the newborn’s blood and fluid taken from the lungs revealed Covid-19 infection.

We report a proven case of transplacental transmission of Sars-CoV-2 from a pregnant woman affected by Covid-19 during late pregnancy to her offspring

More tests showed the virus had spread from the mother’s blood into the placenta, where it replicated and caused inflammation.

Researchers found the baby presented with neurological symptoms associated with infection by the virus, similar to those reported in adult patients.

Neuroimaging analyses indicated white matter injury, which the authors speculate can be caused by vascular inflammation induced by Sars-CoV-2 infection.

Both mother and child recovered from the infection and were later discharged from hospital.

Daniele De Luca, medical director of paediatrics and neonatal critical care at the Antoine Beclere hospital in Paris, and his colleagues measured higher viral loads in the placenta than in the amniotic fluid and maternal blood, which suggests that Sars-CoV-2 might actively replicate in placental cells.

By confirming the presence of Sars-CoV-2 in the placental tissue, and the maternal and neonatal blood, the researchers say transmission from mother to baby most likely occurred through the placenta.

But they say that further studies will be needed to confirm these results.

Writing in Nature Communications, they say: “We report a proven case of transplacental transmission of Sars-CoV-2 from a pregnant woman affected by Covid-19 during late pregnancy to her offspring.

“Other cases of potential perinatal transmission have recently been described, but presented several unaddressed issues.”

They add: “In conclusion, we have demonstrated that the transplacental transmission of Sars-CoV-2 infection is possible during the last weeks of pregnancy.

“Transplacental transmission may cause placental inflammation and neonatal viremia.

“Neurological symptoms due to cerebral vasculitis may also be associated.”