Everything about Jennifer Gentry's second pregnancy was textbook. The birth was fine too.
Mrs Gentry and her husband Nigel welcomed a beautiful and healthy baby boy, Sam, into the world; or so they thought.
Four months after the birth their world came crashing down, again.
"Sam was fine and then at four months I was breastfeeding him and he started having spasms and I knew exactly what they were," Mrs Gentry said.
That was because Sam's older sister, Amelia, was severely ill with a type of epileptic encephalopathy - a rare yet debilitating form of brain disorder that results in aggressive seizures and intellectual disability.
To have a second child with the same disorder was "devastating" for the Canberra family.
"I can still tell you exactly where I was sitting because that feeling was awful, because you just knew what was ahead and how hard it was going to be," said Jennifer.
Sam's diagnosis was also hard to swallow because they had been told by numerous doctors that their chances of having another baby with this condition was slim, around one per cent, as it was thought the genetic mutation that causes the disorder happened spontaneously in the child and couldn't be inherited.
But a genetic breakthrough led by Australian and US researchers has now discovered the chance of recurrence is actually much higher for some.
For the first time, a genetic link has been found between a child with epileptic encephalopathies and either their mother or father.
Researchers at Austin Health and the University of Melbourne, with Dr Heather Mefford and Dr Candace Myers at the University of Washington, studied 123 families looking for the child's genetic mutation in 200 cells of both the mother and the father.
They found in 10 of these families a parent carried low levels of the same mutation.
For these eight per cent of parents, this means that the chances of these parents having another child with epileptic encephalopathies is increased; the more cells carrying the genetic mutation, the greater the recurrence risk.
Published in The New England Journal of Medicine, the findings mean parents can have more accurate genetic counselling when planning a family, says co-author Professor Ingrid Scheffer, Austin Health Director of Paediatrics and University of Melbourne Chair of Paediatric Neurology.
"These results provide support for targeted, high-coverage testing of parents who have a child with a diagnosis of developmental and epileptic encephalopathy. This testing will be helpful in counselling parents regarding the risk of recurrence," Prof Scheffer said.
It's also thought the "exciting" finding could have much broader implications.
"I suspect for other diseases where a new mutation causes severe disease that the parent might actually be carrying it at low levels, I think this finding may have greater impact than just in the epilepsy," Prof Scheffer said.
While it doesn't change the circumstances for Mr and Mrs Gentry, they're pleased for those facing a similar situation.
"We didn't know, but you definitely want to know because these conditions are devastating," Mrs Gentry said.
