A Covid-19 sufferer gave birth to a baby who had antibodies but no trace of the virus.
The Singapore mother, who had the coronavirus in March when she was pregnant, said her son was born without the infection.
But it is not known whether the antibodies will protect the newborn against the disease.
City-state doctors are now studying the impact of Covid on unborn babies.
It comes amid a worldwide effort to better understand whether the infection or antibodies can be transmitted during pregnancy.
Medics are trying to find out if pregnancy offers an effective shield against the virus.
Tan Hak Koon, Chair of the Department of Obstetrics and Gynecology at KK Women’s and Children’s Hospital, said: “It is still unknown whether the presence of these antibodies in a newborn provides some degree of protection against Covid-19 infection, allow the duration of protection. ”
He said there was evidence that antibodies could pass through the placenta to the baby during pregnancy.
Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, described it as encouraging.
He said it added to wider evidence that they provide some protection against the virus.
The expert continued, “Millions of people have been infected worldwide, including probably thousands of pregnant women, with very few reports of infections in very young babies.
“This suggests there may be some protection against maternal antibodies and breastfeeding.”
World Health Organization employers say some pregnant women have an increased risk of developing severe Covid.
But they added that it is not yet known whether an infected pregnant woman can pass the virus on to her fetus or baby during pregnancy or delivery.
Doctors in China have reported the detection and decrease of antibodies over time in babies born to women with the disease.
While evidence transmission during pregnancy is rare, a study in Italy suggested it is possible, according to research published in the Nature journal in October.
Other studies have shown that antibodies can be passed on to a child through breastfeeding.