"Parents need to know." Mum's car seat warning after newborn stops breathing.

A mum in the UK has a warning for parents after her newborn stopped breathing following a long car ride.

When Kirsti Clark, 28, and Christopher Clark, 29, put their three-week-old daughter Harper down on a playmat after a two-hour car trip, the baby’s lips turned blue and she began frothing at the mouth, Daily Mail reports.

“My husband got Harper out [of the car] and put her on his knee but she looked like she couldn’t get comfy so he laid her down on her mat and she was kicking about,” Kirsti said.

“I told him her lips looked blue and then he pointed out how red her cheeks were. He picked her up and I could tell straight away from his face that something was wrong.”

Kirsti hoped Harper was simply holding her breath like she sometimes does while feeding. The pair tried blowing into Harper’s face to break her out of it, but soon white foam “started coming out her nose and mouth”.

“It was so scary. My husband was holding her and patting her back and I was trying to get her mouth open to make sure she didn’t swallow her tongue but her jaw was clenched shut,” Kirsti said.

After rushing her to hospital, medics thankfully resuscitated little Harper who’d had a seizure, advising Kirsti and Christopher that when newborns spend more than an hour in a car seat it can impact their oxygen levels.

“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,” Kirsti said.

“When the consultant told us it was the car seat I couldn’t believe it. I thought ‘there’s no way’. I couldn’t understand why nobody had ever told us.”

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According to 2016 research out of the UK, the angle at which babies are harnessed in car seats, along with the constant vibration of the car beneath them, can cause negative cardiorespiratory effects in newborns.

Professor Peter Fleming, who was involved in the research and was also the first researcher to link a baby’s sleeping position to Sudden Infant Death Syndrome, told the ABC in a 2016 interview that long car rides with newborns should be avoided.

“Car seats are essential in protecting against the risk of accidents,” he said.

“But newborns should only be left in car for as short as period as possible. If possible parents should avoid any long trips – anything over an hour.”

Kirsti and Christopher are speaking out to warn parents because, until it happened to Harper, they had no idea car rides with little ones could be so dangerous.

“Parents need to know. Just two hours in a car seat and we could have lost her, it’s terrifying,” Kirsti said.

“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.”