Pregnant women with COVID-19 do not get more sick than the wider population, according to a Singapore study published on Friday, which also found that babies born to infected mothers have antibodies against the novel coronavirus.

The small study of 16 women also found no evidence of virus transmission between mother and baby, offering insights into an area of COVID-19 infection still not well understood globally.

The World Health Organization says pregnant women can be badly affected by some respiratory infections, and that it is not known whether mothers with COVID-19 can pass the virus to their babies during pregnancy or delivery.

"The study results were reassuring," the Singapore Obstetrics and Gynaecology Research Network said in a statement.

"This demonstrates that the incidence and severity of COVID-19 among pregnant women parallels general population trends."

The study said most participants were mildly infected, while more severe reactions occurred in older, overweight women.

None of the women died and all made a full recovery. Two women lost their babies, which researchers said in one case could have been related to virus complications.

Five women had delivered by the time the study was published, and all their babies had antibodies without having been infected by the virus, although the researchers said it is not yet clear what level of protection this may offer.

Further monitoring was required to see if the antibodies decline as the babies grow, the researchers said.

The number of antibodies in the babies varied and was higher among those whose mothers had been infected nearer to the time of delivery, the researchers added.

Doctors in China have reported the detection and decline over time of COVID-19 antibodies in babies born to women with the coronavirus disease, according to an article published in October in the Emerging Infectious Diseases journal.