Doctors have issued an urgent warning to any pregnant Australian women who are not yet vaccinated against COVID-19.
Obstetrician Dr Fiona Langdon says women who are expecting are extremely vulnerable.
"It is a really dangerous disease in pregnancy," Dr Langdon said.
"During pregnancy, our immune system becomes really sleepy, so when we do catch infections like COVID our body can't mount the same immune response."
Data from the US have revealed pregnant women who catch the Delta variant have a one-in-36 chance of having a stillborn baby.
"At the moment in the UK where there is a huge amount of disease – one in six people in the ICU is a pregnant unvaccinated woman," said Dr Langdon.
Alex Smith, who is a science teacher and new mum to five-week-old Walter, told 9News her decision to get vaccinated during pregnancy was simple.
"If there was a premature delivery or god forbid he passed away — to know I could have done something, I don't know how I would have coped," she said.
Another mother, Eliza, is pregnant with her fourth child and was vaccinated at 14 weeks.
She's relieved she will pass on protective antibodies to her baby.
"(I'm) just really thankful that it isn't something I have to worry about anymore," she said.
"I'm protected should there be an outbreak and my baby is protected."
Doctors are urging women who are hesitant to come forward for vaccination as soon as possible.
"These are extremely safe vaccines and there is absolutely no reason not to go and get yourself one," Australian Medical Association president Dr Omar Khorshid said.