'Severe breathlessness': Young mum paralysed after medical episode

She's also facing the prospect of a lung transplant, but will first undergo rehabilitation after a life support machine left her paralysed below the chest.

Friends and family rallied for the 30-year-old Kurri Kurri, NSW, resident, who had a cardiac arrest while at hospital.

A boot camp fundraiser will be held at Adamstown, Newcastle, next week to help her and fiance Joel Hammond and their 18-month-old son Reid.

In early December, the couple were set to announce their second pregnancy.

"I started suffering from severe breathlessness," Ms Roberts said in a social media post.

"I could not even pick up Reid or put him in the car."

An ambulance took her to Maitland Hospital for tests, but she was soon moved to John Hunter.

She was diagnosed with a severe case of pulmonary hypertension, a type of high blood pressure that affects arteries in the lungs and heart.

She was advised to terminate her pregnancy over concerns it would threaten her life.

"She was 10 weeks pregnant when they diagnosed her. It's a risky disease for pregnancy with a low survival rate," sister Cassidy Roberts said.

"They think she had it before she had her son, so they are both lucky to be here."

Ms Roberts was flown to Royal Prince Alfred Hospital in Sydney and later moved to St Vincent's Hospital.

She had a cardiac arrest while undergoing a medical procedure.

"She was having a camera put through her groin to look into her lungs," Cassidy said.

"They put her on an ECMO machine for heart and lung life support. It takes over the body's blood flow," she said.

"It missed a section of her spine, so she had no blood flow to that part. She has a spinal cord injury from that."

While on life support, she miscarried her baby.

Cassidy said doctors had planned to give her sister a lung transplant.

"But the fact she is now paralysed means for the time being she has a PICC (peripherally inserted central catheter) with constant medication flowing through her.

"They're hoping they can avoid a transplant, at least for the time being.

"There's a possibility down the track she will need one. They don't know if the medication will be sustainable forever."

She will be at St Vincent's for at least a month.

"Then she'll go to a rehab centre in Sydney for a few months," she said.

Maddison and her family had been inundated with messages of love and support, for which they were "beyond grateful".

"It just goes to show how loved our Maddi is, and my god she is loved," Mr Hammond wrote in a touching tribute on social media.

In another heartfelt post, Cassidy told Maddison "I need you to know that I really couldnt live without you".

Cassidy told the ACM's Newcastle Herald it had been an "emotional rollercoaster".

"It came out of nowhere. We didn't think it would be what it turned out to be," she said.

A Gofundme was created that hit its target of $35,000.

The next step is the boot camp fundraiser, which friends Cassandra Shepherd and Kelsie Grezl organised.

Ms Shepherd said she wanted to help Maddison "in her time of need".

"She's a great friend who has always offered support. She's greatly appreciated."

The boot camp, to be held at KIN Health Co at Adamstown on Saturday, January 25, costs $10.