"The car journey was horrendous. I was trying to make sure she was breathing but I was shaking so much I couldn’t tell,” Kirsti recounted.
"When we got to the hospital I ran in with her in my arms. I was hysterical and crying, I shouted ‘please, please help her’ I think I scared the receptionist.”
As Mail Online reports, the little girl had suffered a seizure, but doctors managed to get her breathing again.
Consultants warned the parents that babies kept in a car seat more than one hour could suffer oxygen deprivation.
Kirsti has since spoken out about the terrifying ordeal in order to warn parents about the potential dangers of having a baby in a car seat for even a short period of time.
"That’s why we knew we had to share what happened to Harper because parents need to know. Just two hours in a car seat and we could have lost her, it’s terrifying," she told Metro
"I would tell every parent to just really carefully watch their babies and if they don’t absolutely need to be in the car seat take them out because it is not worth what we had to go through.
"Watch your baby and know your baby. If something doesn’t seem quite right take them straight to hospital."
You can find more information about how to use car seats correctly in Australia, and regulations about forward-facing, rear facing and booster seats via The Child Car Seats website.