Sonya and Youssef Ghanem went to Sydney's Bankstown-Lidcombe Hospital in July 2016 expecting to bring home a little brother for their three children.
Instead, their baby John died 57 minutes after he was born.
Their grief was compounded when they learned their newborn had been ventilated not with oxygen, as the operating theatre's gas outlet was labelled - but instead with nitrous oxide, or laughing gas.
Their child was not the first victim of the mix-up, which the hospital would take almost a week to rectify once a nurse raised her concerns.
An inquest is now underway into John's death.
"One can't truly understand what it must have been like for the Ghanem family as they both grieved the loss of their child and came to learn about the shocking chain of events at Bankstown-Lidcombe Hospital that led to his death," counsel assisting the inquest, Donna Ward, said on Monday.
John was in trouble when he was born by emergency caesarean section.
He gave only a weak cry and was not breathing properly when he was delivered in the hospital's Operating Theatre 8 at 11.54am.
But doctors moved quickly to resuscitate him, first rubbing him with a cloth then applying a face mask for newborns.
When pumping room air into his lungs was not enough to get him to breathe on his own, the team moved to ventilate him with what they believed was 100 per cent oxygen.
As the baby's heart rate continued to drop, doctors performed CPR and administered adrenaline - to no avail.
He was declared dead at 12.51pm.
"Sonya and Youssef got to spend time with their baby boy, but this was after John had died," Ms Ward said.
The death made no sense to the resuscitation team, who believed they'd done everything right. An autopsy did not reveal any congenital problems that would explain the death.
Then a doctor's hunch kicked in.
Paediatrican Dr Phillip Emder had treated another newborn, Amelia Khan, in the same operating theatre just weeks earlier.
He'd tried to resuscitate her with oxygen. Like baby John, she hadn't responded as expected. She'd started to breathe on her own only after he'd connected the resuscitation device to another machine.
Amelia has been left with severe brain damage.
After reading about an incident in India where a child was administered nitrous oxide instead of oxygen, Dr Emder raised his concerns with a nurse who'd helped to resuscitate Amelia.
She requested that the operating theatre's gas outlets be tested, expecting her concern to be actioned within four hours.
Instead it took nearly a week and nudge from the nurse for Dr Emder's hunch to be confirmed.
There was no oxygen coming from the oxygen outlet in Operating Theatre 8 - instead, it was nitrous oxide.
The mix-up meant that John never had a chance to respond to the "significant clinical effort" to revive him, Ms Ward said.
Gas fitter Christopher Turner has already pleaded guilty to breaching to the NSW Work Health and Safety Act. The NSW District Court fined him $100,000 in 2020.
The inquest will also look at testing of the gas pipes, which were wrongly installed almost exactly a year before John's death.
It appears testing was "not adequate", Ms Ward said.
A statewide investigation in 2016 revealed the hospital's Operating Theatre 8 was the only place in NSW where medical gases were incorrectly piped.
The inquest at the NSW Coroners Court is expected to last for two weeks.