Jean and Stephen Nowlan, from Saggart in Co Dublin, were warned that Pierce might not survive and that the high risk of cerebral bleeds in premature infants could have fatal consequences for him.

"It is absolutely heartbreaking to think that he survived all that and grew to be a robust healthy two-year-old, only for this to happen and for him to die on an operating table during a standard procedure, " Jean Nowlan told the Sunday Tribune yesterday. "He was our one and only, our first [child]. Everything revolved around him and that was all taken away the day he died."

The Dublin city coroner last Friday recorded a verdict of death by medical misadventure in Pierce's case. The little boy was admitted to Our Lady's Hospital on 11 October 2004, his second birthday, to have a device fitted into a vein that would have allowed the regular injection of a blood-clotting agent. During the procedure, an artery was punctured and he died three days later from brain damage.

His parents fought successfully for an amendment to the Coroner's Act that allowed only two medical practitioners to give evidence at an inquest. The hospital also carried out an internal review after Pierce's death and has since changed the procedures of that operation.

"It was a terrible, arduous process and a bit drastic that we had to get a law change in order to find out what happened to our son, " Pierce's mother said. "We went through supreme effort to get that law changed and had no privacy to grieve. But there were 23 clinical personnel present at the time and several different versions of the event. We had to find out what happened."

The Nowlans said they are relieved at the coroner's verdict of death by medical misadventure, but feel they should never have had to go through this process to get it. The hospital, Jean Nowlan said, didn't explain the procedure properly and failed to tell them there was an alternative way of doing it. They are now considering taking legal action against the hospital.

"If the hospital had just told us back in October 2004 what had happened, I think we could have accepted it and moved on, " Nowlan said. "Instead, we had to go through the courts and hear about what happened to him in dribs and drabs. Each revelation was hurtful. I have had to relive what happened to Pierce so many times."

When the Nowlans were first told Pierce had haemophilia, just a week after he was born, they were "devastated". There was no history of the condition in their families and for the first few months they were especially fearful of something happening to him. But Pierce grew into a healthy and happy toddler, the image of his father and always smiling.

The day Pierce died, his mother said, "my life just fell apart. Children are absolutely everything to you and suddenly, he was gone. We had to go home to an empty house and try and rebuild our life. But then, we couldn't even do that because we had to start fighting to find out what happened.

"We have had to try and come to terms with his death, but this delayed the healing process. Now that it's over, we have to try and get on with our life. That's the biggest challenge now. We don't want to move on, but we have to.

"My sister told me yesterday to hold on to the fact that we did something amazing and that doctors know they are more accountable now because of Pierce, " Jean Nowlan said. "We did it in honour of him. We're just ordinary people. We never dreamt that something like this could happen to us."