Four days into her stay – on September 1, 2013 – by caesarean section, she gave birth to Nicholas, who weighed roughly the same as a fully-grown human brain (1.56 kilograms), and was 41cm long.

"We had very little time to assimilate what was happening. We were planning to watch the finale of MasterChef that night and instead we had a baby," Mr Brennan, the deputy high commissioner at the British High Commission, said.

Without attending their check-up they "would've had no inkling that anything was wrong and that could have been horrible".

Premature birth is the most common killer of newborns and about 15 per cent of all babies are admitted into neonatal intensive and special care units every year in Australia – more than 115 each day.

"It was scary, because they don't have any fat on them – and all you see is just skin and bones ... You wonder whether he is going to survive," Mrs Brennan said.

Nicholas spent nearly two months in the hospital, but the 14 days on the incubator were the toughest as his parents couldn't cuddle their tiny bundle of joy.

"You don't see the baby immediately and that was the difficult thing for me," Mrs Brennan said.

Other mothers in the ward had tears of guilt, felt a loss of connection with their newborns and became depressed from the detachment, she explained.

"I can see why this happens to some people, it's really hard."

Once Nicholas moved from intensive care into special care (with an open cot), Mrs Brennan took milk into hospital three to four times a day, "stressing he wouldn't have enough".

They credited Nicholas's healthy recovery – which required just one common operation – to the "brilliant staff" at The Canberra Hospital, the "absolutely amazing" ACT Health workers and the "helpful" midwives who regularly visited.

The first time the Forest family participated in Life's Little Treasures' Walk for Prems, Mr Brennan said three-week-old Nicholas was "probably the smallest person at the course". They'll again be walking around Lake Tuggeranong for the October 25 event, which has nationally raised $42,900 so far.

"Canberra is such a small community that people get to know about these things. It's important to get the word out there because there are so many people who don't get the support, like regional families travelling long distances to hospital," Mrs Brennan said.

For information on Canberra's Walk for Prems, visit walkforprems.org.au/locations/canberra/