There's new hope for thousands of families who live in fear of passing on diseases from one generation to another.
For the first time, scientists have successfully repaired a faulty gene in human embryos using a process known as "gene editing".
Nicole Mowbray has a genetic disease that affects her heart and puts her life at risk.
There's a 50 per cent chance she could pass it on if she decides to have children.
"We don't want to pass on something that caused my child to have a limited life or a painful life or a life of risk. I mean that does obviously come to the front of my mind when I think about having children," she said.
But now Korean and US researchers have found a way to prevent the condition from being passed to the next generation, by using a technique called crispr to alter the genetic code of a human embryo.
"I'm sitting here as a geneticist gob smacked that we're talking about precisely editing the human genome in this manner," said Professor Stephen Robertson, a University of Otago geneticist.
It's a technique that could lead to the eradication of dozens of genetic diseases.
This study represents a start. But by no means are we near a clinical end point."
Professor Stephen Robertson, University of Otago geneticist
Current IVF treatments prevent some hereditary diseases by screening out affected embryos.
This new technique takes it further by repairing the damage in them, but it's still a long way off general use.
"This study represents a start. But by no means are we near a clinical end point that we can say with confidence that actually we can alter a person's genome for their benefit and for negligible risk," Professor Robertson said.
These sort of ethical discussions can't happen quickly enough"
Dr Jeanne Snelling, medical ethics and legal specialist
Along with that risk comes numerous ethical and legal hurdles.
Current legislation in New Zealand prohibits implanting anything that has been genetically modified, so at the moment, no one is allowed to have a genetically edited embryo implanted inside them.
Dr Jeanne Snelling, a medical ethics and legal specialist, said the technology is developing rapidly, "so these sort of ethical discussions can't happen quickly enough really".
Professor Robertson said: "The questions are well defined, I think, and the risks are certainly clear in front of our nose. And we need to address them rigorously before we take steps forward to introduce this stuff into the clinic."
It may be a medical breakthrough, but real world application, especially here in New Zealand, still some way off.