A nurse practitioner connected with St Michael's Hospital in Bristol, UK could face legal action for taking off a premature baby from a ventilator without explicit permission and instruction from the doctors.

Baby Rohan Rhodes was born very premature at 25 weeks to parents Alex Rhodes and Bronwyn Vincent at Singleton Hospital in Swansea. Although premature, his mother said his lungs were holding up well. However, he had to be transferred to St Michael's Hospital to undergo heart surgery to increase his chances of survival.

But since born premature, a ventilator is essential to help Baby Rohan fill his lungs with oxygen.

Doctors at St Michael's Hospital conferred the minute baby Rohan was transferred to the facility that he would stay on the ventilator until he had his operation.

"Our little boy was doing so well. We are still trying to understand why this nurse did what she did. She had no authority. What she did is inexcusable. I was in tears," Ms Vincent said. "When we arrived at St Michael's his life wasn't in danger even though he was in intensive care."

Baby Rohan developed necrotising enterocolitis (NEC), a fatal condition common in premature babies, after being taken off the ventilator. He had a series of cardiac arrests and died the following day.

Ms Vincent said doctors even assured them their son's prospects were good once the heart surgery has been conducted.

"We have no idea why the nurse did what she did - but we are convinced it cost our son his life."

"Nurses can only take a baby off a ventilator under a doctor's direction and we know there wasn't a doctor's decision to do this," Ms Vincent said.

Adding more insult to injury was that the nurse even received further training despite the incident. She also remains connected with the hospital.

It was also said the tragedy has not been reported to the Nursing and Midwifery Council. The body has the authority to hold a hearing and remove her from the nursing register.

It was also believed the nurse has yet to be disciplined for the blunder which occurred on August 2012.

An inquest will convene on Monday to hear the circumstances that led to baby Rohan's death.