SINGAPORE - Will Covid-19 mRNA vaccines harm the foetus? Are booster shots recommended for pregnant women? These were some questions raised by pregnant women and members of the public during a webinar on Saturday (Oct 16) organised by the College of Clinician Scientists under the Academy of Medicine Singapore.

Here are some questions answered by doctors.

Q: Why are unvaccinated pregnant women at higher risk of Covid-19 complications?

A: Unvaccinated pregnant women - especially those at the later stages of their pregnancy and who have pre-existing medical conditions - are at higher risk of needing intensive care or mechanical ventilation, should they contract Covid-19. During the later stages of pregnancy, the growing foetus may press the uterus against the diaphragm - a respiratory muscle - causing it to be pushed up slightly, said senior consultant Citra Mattar from the National University Hospital obstetrics and gynaecology (O&G) department's division of maternal foetal medicine.

Covid-19 also significantly increases the risk of pregnant women developing blood clots. A clot in the lungs could be life-threatening, said Professor Tan Hak Koon, KK Women's and Children's Hospital's (KKH) O&G division. "Pregnant women infected with Covid-19 are also twice as likely to deliver preterm because the doctors have to deliver their babies earlier to help their lungs and heart function better," he added.

Q: If mummy gets Covid-19, will the baby get it too?

A: Data from last year and early this year shows that the risk of transmission from pregnant mother to the foetus is about 1 per cent to 4 per cent, said Associate Professor Zubair Amin, head and senior consultant at the neonatology department in the Khoo Teck Puat - National University Children's Medical Institute at the National University Hospital.

"But (recent) anecdotal data is showing that this percentage is probably too low an estimate. It seems that with the (more infectious) Delta variant and the current wave of infections, the risk of transmission is much higher," he added.

Transmission can happen during pregnancy, at the time of delivery, or post delivery during breastfeeding or direct contact.

Babies are at increased risk of admission to the neonatal intensive care unit, so the mothers have to grapple with being separated from their newborns.

Q: How would Covid-19 in pregnant women affect newborns?

A: Children are known to have a lower risk of mortality and severe illness from Covid-19, compared with older people. But infected newborns are at higher risk compared with older children, said Prof Amin.

Existing data shows that babies' risk of mild symptoms such as runny nose and cough is 40 per cent to 50 per cent, while the chance of moderate to severe symptoms such as breathing difficulties and poor feeding is at 12 per cent to 40 per cent.

Moderate and severe complications in an infected newborn would include pneumonia, respiratory distress, vomiting, diarrhoea, occasionally low blood counts and collapsed lungs, said Associate Professor Thoon Koh Cheng, head of the infectious disease service in the department of paediatrics at KK Women's and Children's Hospital. Prof Thoon did not take part in the webinar.

Q: How do mRNA vaccine side effects differ for pregnant women?

A: Side effects, such as sore arm, fever and headaches, are similar to the rest of the population.

But if some women - during the course of pregnancy - are already experiencing severe nausea or are feeling very unwell or very lethargic, they should wait a week or two until those symptoms subside, before getting the vaccine. This is because the vaccine could exacerbate their nausea and morning sickness, for instance, said Associate Professor Mahesh Choolani, president of the College of Clinician Scientists.

"You can get vaccinated when you feel more comfortable, but otherwise, there's no specific complications to getting the vaccination," he added.

Q: Are pregnant women advised to get booster shots?

A: International guidelines are currently recommending that all pregnant women have the booster if fully vaccinated, said Associate Professor Tan Lay Kok, head of the maternal foetal medicine department at KKH.

Currently, eligible people aged 30 and above will be invited to take Covid-19 vaccine booster shots, as long as they have had their second jab at least six months ago.

Some studies have shown that antibodies from vaccinated mothers can be transferred to babies via the placenta or through breast milk.

Prof Tan Lay Kok added: "So there is little reason to suspect anything untoward happening from a booster, and the purpose of the booster is to boost or maintain antibody levels. So if you are eligible for the booster, go for it."