SINGAPORE - Pregnant women infected with Covid-19 are at a higher risk of serious illness and complications, and some may even pass the virus to their babies.

However, those who are vaccinated have a lower risk of catching the coronavirus and could pass on antibodies to their newborn children.

These were the key messages presented by a group of medical experts at a webinar on Saturday (Nov 27).

Jointly organised by the College of Obstetrics and Gynaecologists Singapore (COGS), the Obstetrical and Gynaecological Society of Singapore and the Perinatal Society of Singapore, the session was aimed at addressing concerns that expectant mothers here might have about getting vaccinated.

One of the speakers, Dr Serene Thain, a consultant at the department of maternal foetal medicine in KK Women's and Children's Hospital (KKH), said that in the last month or so, about 98.7 per cent of all local Covid-19 cases were either asymptomatic or mildly symptomatic.

In contrast, international studies show that generally about 79.1 per cent of Covid-19 cases who were pregnant were asymptomatic or mildly symptomatic. This means that 21 per cent either have moderate, severe or critical symptoms as a result of the infection.

Dr Thain added that pregnant women tend to be at higher risk because of the various physiological changes they undergo during pregnancy.

"Pregnancy in itself is already an additional stress on the body, not to mention if there is an additional stressor of Covid-19 infection that is added on to it," she said.

Expectant mothers with Covid-19 are also two to three times more likely to have premature births. This is because doctors often have to deliver the babies of women with severe Covid-19 infection earlier than expected in order to help them recover.

"(For) those with more severe disease or those who require oxygen supplementation or intubation, delivering the baby will help improve the mother's heart and lung functions," Dr Thain explained.

Other issues brought on by infection during pregnancy include doubling the risk of stillbirth, and a 1½ times higher risk of pre-eclampsia, a condition where blood pressure rises and can result in seizures, fits or death in the mother.

Additionally, in about 3 per cent of cases, mothers with Covid-19 may pass the disease to their newborns, said Dr Yeo Kee Thai, consultant at KKH's department of neonatology.

Some babies may go on to develop symptoms such as respiratory failure, feeding difficulties, diarrhoea, vomiting, irritability and lethargy.

But while infected mothers may pass the disease to their newborns, vaccinated mothers can pass antibodies to them, noted Dr Yeo.

Citing several overseas studies, Dr Yeo said antibodies can be transferred through the placenta to the unborn baby, which may protect the child from future infection.

He added: "If you get vaccinated, you would have antibodies being secreted in breast milk. And when the baby drinks the breast milk, we know that potentially it can provide immunity or protection against this infection."

Associate Professor Tan Lay Kok, president of COGS, noted that as at September, more than 85 per cent of pregnant women hospitalised for Covid-19 were unvaccinated.

Of these, 20 per cent experienced severe symptoms and required oxygen, while 10 per cent required care in high dependency wards or the intensive care unit.

KKH saw 91 cases of Covid-19 infected pregnant women from May to end-October, Prof Tan added. Most were in their third trimester, with only 33 per cent fully vaccinated.

Thirteen of the 91 women, none of whom was fully vaccinated, developed pneumonia, he noted.

Prof Tan said many studies have shown that mRNA vaccines, such as those by Moderna and Pfizer-BioNTech, are safe for pregnant women.

"Covid-19 vaccination in pregnancy is safe. Covid-19 infection in pregnancy is not. So, we strongly recommend Covid-19 vaccination for pregnant women using the mRNA vaccines," he added.