When Celine Ng-Chan was 10 weeks pregnant, she was diagnosed with COVID-19. Back then, in March, even less was known about how the coronavirus affected pregnant women and their future children.

But now that Ng-Chan, a private tutor in Singapore, gave birth to her son Aldrin in early November, the news is encouraging both for Ng-Chan and other women who have or contract COVID-19 when pregnant.

Aldrin is COVID-19-free and appears to have acquired protective antibodies at least temporarily from his mother's illness, Ng-Chan told the Straits Times. Ng-Chan wasn't COVID-19 positive during delivery.

"My pregnancy and birth was smooth sailing despite being diagnosed with COVID-19 in my first trimester, which is the most unstable stage of the pregnancy. I'm very blessed to have Aldrin and he came out very healthy," Ng-Chan said. "I feel relieved my COVID-19 journey is finally over now."

Her story adds a face to research suggesting that mother-to-infant COVID-19 transmission is rare, and that babies born to women who've had the illness may be somewhat protected, Dr. Jessica Madden, a paediatrician and neonatologist who serves as medical director of Aeroflow Breastpumps, told Insider.

Some COVID-19 antibodies seem to cross the placenta

Small studies have suggested that COVID-positive mothers pass on IgG antibodies - the type that indicate recovery - against the virus to their fetuses in utero.

One March paper of six women who tested positive for the virus at delivery, for instance, found five of the babies had elevated levels of IgG antibodies even though none had COVID-19. All of the women wore masks, delivered their babies via C-section in negative-pressure isolation rooms, and were isolated from their children immediately after delivery - something more recent research has suggested is unnecessary.

An October case report also describes an infant born to a mum with asymptomatic COVID-19 who had IgG antibodies but a negative COVID test, demonstrating "passive immunity" through the placenta, the authors write.

In some ways, this is expected, since IgG antibodies against other bacteria and viruses are known to protect fetuses and newborns against infectious diseases, Madden told Insider.

"This is the reason why certain vaccines, like pertussis and flu, are recommended during pregnancy," she said. "IgG antibodies increase in fetuses later in pregnancy, especially after the 36-week gestation mark."

Still, more research is needed to understand how severity of illness affects antibody levels, how time of infection during pregnancy plays a role, and how strong and long-lasting babies' presumed immunity is.

One study out of Wuhan, China, including 24 COVID-19-positive pregnant women suggested any immunity in newborns wanes quickly.

What's more, Madden said, "we do not know if having COVID-19 prior to pregnancy will provide IgG immunity to fetuses who are conceived after a mother has already recovered from the virus."

Breast milk has detectable antibodies too

The breast milk of mums recently infected with COVID-19 is also believed to offer some protection to newborns. One preprint study in September showed that of 37 milk samples, none had detectable virus but all had antibodies thought to neutralise COVID-19.

This too isn't entirely surprising since some breast milk antibodies are known to help protect babies from various diseases like measles while they're too young to receive a vaccine. Breastfeeding is also associated with a lower risk of conditions including diabetes, asthma, sudden infant death syndrome, and some gastrointestinal illnesses.

Those benefits outweigh the still-yet-unseen risks of breastfeeding with COVID-19, according to top health organisations like the Centres for Disease Control and Prevention, as long as new mums with the illness take precautions like wearing a mask and washing their hands and breasts before nursing.

This article was originally published by Business Insider.

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