The world-first trial, Mackenzie's Mission, aims to identify couples with a high chance of having a child affected by one of 750 severe genetic conditions.

Researchers hope the trial paves the way for a roll out of testing for all Australian couples who wish to have it.

Last week, Fabieli Parronchi and her husband Antonio became the first Canberrans to take part in the study, which involves a simple cheek swab.

They have a three-month-old son Antonio and are looking to expand their family.

They are yet to receive the results but are thankful for the extra knowledge it will give them.

"When you are trying to have a baby, your biggest wish is that your baby's healthy. Anything that can help you with that is a big advantage," Mrs Parronchi said.

"I think it would be amazing if the government could offer that opportunity for people who are trying to get pregnant.

"I'm originally from Brazil and I would have never had the opportunity to do this there."

Canberra obstetrician Stephen Robson is leading the recruitment of local families.

He said researchers expected about one or two couples in every 100 will find they carry a potential mutation between them.

"We can tell them all about their genetics, it's such a deceptively simple test to have," professor Robson said.

"This study is being watched closely by doctors and scientists around the world. It's very exciting that prospective Canberra parents can be part of cutting-edge research."

As part of the study, testing is free and genetic counselling is available for couples who find they might carry a gene for childhood disease.

The study has now progressed from the pilot stage with couples being referred in Victoria, Western Australia, NSW and the ACT. It will extend to couples in Tasmania, South Australia, Northern Territory and Queensland next year.

One of the lead investigators in the study, professor Edwin Kirk, said researchers aimed to test 10,000 couples from every part of Australia.

"Those couples who find they have an increased chance of having a child affected by one of these conditions will have choices that they would not otherwise have had," he said.

The $20 million federally-funded study was prompted by a campaign from Rachael and Jonathan Casella, whose daughter Mackenzie died in her first year of life from spinal muscular atrophy.

Her parents were both healthy carriers of the genetic mutation that leads to spinal muscular atrophy, but were unaware.