Clementine and Felix Widdup were born 13 weeks early weighing less than a kilogram, after their mother Georgia got the pregnancy complication preeclampsia.

"They were in hospital for three months, the babies were pretty sick for a pretty long time," Ms Widdup told AAP.

Nine years later, she still has a sense of amazement that her twins are healthy and living normal lives, thanks to the care they received at the Royal Women's in Melbourne in 2012.

"It's really been beyond our wildest dreams because they were so small and so unwell, I don't think we really imagined that they could be as healthy as they are now," Ms Widdup said.

The twins left their own tiny legacy from their time in the neonatal intensive care unit, after the Widdup family gave permission for Clementine to participate in a medical trial - the results of which should reduce the risk of lung problems in other pre-term babies.

Clementine was one of almost 500 premature babies to take part in an international study dubbed OPTIMIST-A, which trialled using a tiny catheter to deliver an essential substance into the babies' lungs.

Pre-term babies lack a substance called surfactant in their lungs when they are first born, which is needed to keep their lungs supplying oxygen.

The surfactant can be delivered through a tube sent through the vocal cords and into the windpipe, often before babies are hooked up to a ventilator.

But this process can lead to problems down the track.

A CPAP machine, which delivers a steam of constant oxygenated air, is a less invasive option than ventilation, but without intubation there's no way to deliver the much-needed lung surfactant.

So doctors adapted a thin, bendy catheter from adult intensive care units, and tried using it to administer the surfactant - with much success.

"The cunning plan was to find a way of getting surfactant into these babies while they were still on CPAP, that's where this new catheter came in," Professor Peter Davis from the Royal Women's Hospital told AAP.

The babies spent less time in intensive care and were half as likely to need a ventilator in their first three days, while the risk of chronic lung disease was also reduced.

"There's no silver bullet for these little babies, but it's an important part of the puzzle," Prof Davis said.

The catheter method was developed by Tasmanian specialist Professor Peter Dargaville.

"Our results suggest that the use of the 'Hobart method' for giving surfactant on day one will translate into a healthier start to life for premature infants around the world," he said.

Georgia Widdup said she was simply happy her family could play a part in improving treatments for pre-term babies in future.

"I very much felt when our kids were in hospital, we were standing on the shoulders of other people who had participated in trials and research along the way," she said.

The trial started at Royal Hobart Hospital in 2011 before expanding to the Royal Women's in 2012, while hospitals in the UK, USA, Canada, Israel, New Zealand and the Netherlands also took part.

The OPTIMIST-A trial has been published in the Journal of the American Medical Association (JAMA).