Australia’s cautious approach is similar to that of the UK, where parliament voted in 2015 to legalise mitochondrial donation. There, only one clinic, the Newcastle Fertility Centre, is licensed to perform the procedure. It must call on the UK’s fertility agency, the Human Fertilisation and Embryology Authority, to approve patients on a case-by-case basis.

Under new Australian law, mitochondrial donation will initially be offered at a fertility clinic as part of a clinical trial. The trial probably won’t start for another year or two, and once it does, it’s expected to last 10 to 12 years. Families interested in participating in the trial will need to attend a consultation to discuss the potential risks involved in mitochondrial donation, and participants will ultimately need to be approved by an expert committee.

The law requires researchers to track the participants’ pregnancy and birth outcomes, including any miscarriages, premature births, birth defects or mitochondrial diseases in babies born to those pregnancies. Investigators will also monitor the ongoing health and development of children born as a result of the trial.

Unlike UK law, Australian children born through this procedure will be able to access identifying information about the egg donor in the same way as children born through egg donation.

The number of participants in the trial has not been determined, but according to the Australian government’s April 10 funding announcement, the trial must “provide access to the technology for affected families”. Megan Munsie, a stem cell scientist and professor of emerging technologies at the University of Melbourne, said that while about one in 5,000 babies are born in Australia with a severely disabling mitochondrial disease, not all women with mitochondrial disease need to use this technology.

“This reform rightly limits the use of mitochondrial donation, the only option available to them, to reduce the risk of a woman’s child inheriting a mitochondrial DNA disorder that can lead to serious disease,” she said. “Depending on how the disease affects their mitochondria, other assisted reproductive technologies, such as preimplantation genetic testing, may suffice.” This type of testing allows prospective parents through IVF to select only healthy embryos for implantation.

Even after the trial period in Australia ended, women with mitochondrial DNA mutations were not able to use the technology more widely. “It is uncertain whether this technology will be implemented clinically,” said Catherine Mills, director of the Monash Centre for Bioethics in Australia. It will depend on the results of clinical trials, which will weigh safety and efficacy.

There are two main safety concerns with the procedure, says David Thorburn, a mitochondrial disease researcher at the Murdoch Children’s Research Institute in Melbourne. One is that a small amount of “carry” mitochondrial DNA from the mother may end up in the baby. “During development, this can increase to higher numbers, which can lead to mitochondrial disease,” he said.