Genetic carrier screening: national study backs expanding testing for parents-to-be

Aspiring parents can scan for hundreds of genetic conditions before having children, but only three are covered by Medicare. New research suggests that should change.

More than 9000 Australian couples have been screened for hundreds of genetic conditions, in a bid to reduce the risk of passing on life-threatening illnesses to their future children. 

Couples were tested to see if they had an increased chance of having children with one or more of about 750 severe genetic conditions, in the largest screening project ever undertaken in Australia – and one of the first of this scale in the world. 

The government-funded project, Mackenzie’s Mission, demonstrated the feasibility of setting up a significantly expanded national screening program and provided insights into how couples respond to such screening. 

The project, administered by Australian Genomics, tested 9107 couples, of which 175 were found to have an increased chance of having children with a severe genetic condition. The findings were published in The New England Journal of Medicine on Thursday. 

Three-quarters of those couples then used that information to inform their decisions about having children, including using IVF and selecting embryos unaffected by the genetic condition.

The project was led by Conjoint Professor Edwin Kirk, of UNSW Sydney and NSW Health Pathology, Professor Martin Delatycki from Victoria Clinical Genetic Services and Murdoch Children’s Research Institute, and Emeritus Professor Nigel Laing from The University of Western Australia and PathWest Laboratory Medicine. 

Reproductive genetic carrier screening in Australia

The findings come after reproductive genetic carrier screening (RGCS) for three conditions – spinal muscular atrophy, cystic fibrosis and fragile X syndrome – was added to the Medicare Benefits Schedule last year, making Australia one of the few countries to fund free RGCS.

While this was a welcome step forward, the majority of conditions identified by the study would not be picked up by the existing Medicare-funded screening, said Prof. Kirk. 

“Eighty per cent of the couples identified in our study as having an increased chance for one of the screened conditions would not have been identified by the test now funded under Medicare.”

While RGCS is becoming more widely understood, it is still not routinely offered by all healthcare practitioners and expanded carrier screening – covering hundreds of genes rather than three – is only available on a fee-paying basis through a growing number of commercial providers. This means it is only available to those who can afford it.

Prof. Delatycki said the study showed many couples embrace such screening when given the chance. 

 “Most of those who find they have an increased chance of having children with a serious condition take steps to avoid this.”

The Mackenzie’s Mission project set out to find answers to many of the challenges involved in setting up a national program, including how to best offer it at population level, which genes to include, how laboratories report results, how couples respond once they discover they are at increased chance of having children affected by one of the conditions, and costs.

“Our goal was to study how best to deliver reproductive genetic carrier screening for the Australian population, and the project taught us a great deal. As a result, we are well positioned to take the next step to a national program,” Prof. Kirk said.

“We look forward to continuing to work with the government towards a fully funded screening program, so all Australians can have access to broad reproductive genetic carrier screening should they wish to.”

About the Mackenzie’s Mission project

The project is named after Rachael and Jonathan Casella’s daughter Mackenzie, who died in 2017 from spinal muscular atrophy (SMA), a severe inherited neuromuscular condition without a cure. She was only seven months old. 

Neither Rachael nor Jonathan have the condition, but both are carriers with a one in four chance of having a child with SMA – something they only discovered after Mackenzie was born.

Mackenzie’s journey was the catalyst for a campaign by Rachael and Jonathan to call for routine reproductive genetic carrier screening free for all prospective parents in Australia. 

Until recent years, parents would only learn of their carrier status after the birth of an affected child, as Rachael and Jonathan did. RGCS gives couples the choice to have that information before or during early pregnancy.