On Tuesday, doctors in France said they had confirmed a case where transmission occurred in a baby boy born in March with brain swelling and neurological symptoms from which he later recovered.
But the overall prevalence of such transmission is thought to be extremely rare -- on the order of two percent or less.
Foetuses are rarely infected with Covid-19 because the placenta produces very small amounts of the receptor that the coronavirus latches on to when it invades human cells, according to a study.
The placenta plays a role in stopping harmful substances from being passed down from a mother to her unborn child -- but certain pathogens like the Zika virus are known to cross this barrier frequently.
