In the fourth of a monthly series, Sharon Dempsey tells of the night she was told her son Owen was gravely ill.

I have spent the weekend with my two best friends, Deborah and Zoe, and their children. They came to Belfast from Cardiff where we lived until Owen, my son, was diagnosed with a brain tumour at the age of two and four months.

Deborah and I met at National Childbirth Trust classes 11 years ago when we were pregnant with our first babies, Kate and Amy. We bonded over a fear of episiotomies and a distrust of the NCT teacher's description of childbirth as being merely uncomfortable. Zoe was a friend of Deborah's and was pregnant with Holly. The three of us became close. Our children were like cousins, growing and playing together.

They have visited Belfast several times and know my extended family well. Deborah's son Ben is my godson. He and Owen would be the same age. I dreaded seeing him again. He was the only boy in the gang of girls, Kate, Amy, Holly and Daisy. Owen's absence was tangible to all.

My current pregnancy seems a world apart from my first when in Cardiff everything was full of possibility and hope. I had no sense then of what was to come.

I was at Zoe's house on the day of Owen's diagnosis. He had been unwell, a vague viral-like illness that the GP was unconcerned about but which had worried me all week. By the Friday he seemed a lot better and we called to visit Zoe.

At Zoe's he began walking with his head to one side and was unsteady on his feet. Zoe assumed it was an ear infection and called the GP's surgery to get an appointment for after lunch. Owen and I went home and I phoned my mum.

Her advice was to just go to the hospital. My neighbour was a nurse, so I rang her. She didn't give me an option - within minutes she was at my front door with the car running. We rushed off with Owen's comforter, my old satin nightie and his bottle in case it was a long haul. It was three weeks before we were home again and in that time everything in our lives had changed beyond recognition.

At the hospital, Owen co-operated with all the neurological tests, bemused to be entertained by a variety of medics. He didn't seem to be in any pain or discomfort unless walking but every so often he would say, "mum, mum, hug".

He would fold into me and we would snuggle together, his soft curly blond hair just below my chin.

I was asked about his medical history several times - he had had a long birth, was breast-fed until 11 months, was hospitalised with breathing difficulties at four weeks; from a year old he had a pattern of repeated viruses, and he was reluctant to try new foods.

I had taken him to the GP frequently and at around 16 months he had seen a hospital paediatrician who had tested him for every illness from coeliac disease, which I have, to liver function and thyroid problems.

There was no reason to look for something neurological. He was a bright, affectionate child who had reached all his milestones on target.

I phoned Liam at work and told him to meet me at the hospital and that so far all I had been told by a registrar was that there could be something seriously wrong with Owen's brain. Despite all our worrying, this seemed far-fetched.

Although Liam and I worried about him constantly, it was from a sense of unease rather than particular symptoms. On the last visit to the GP during the week of the diagnosis I had asked for a further referral to the paediatrician. The GP didn't think it was necessary and asked why; my answer was simply "because he is too good". He wasn't climbing or playing with the same robustness as other two-year-olds. I couldn't explain my deepest fear that Owen wasn't going to be with me forever.

Owen had been sedated to enable a CT scan to take place. We had watched as he was laid out on a trolley, still and pale with a hospital gown on, waiting for the scanner to rotate around him. It was a foreboding image which stayed with us throughout the years.

We were told the devastating news around nine o'clock on that Friday night in a room separate from our sleeping son. There were about five medics seated facing us while the consultant explained slowly and quietly what they had discovered. The scan revealed a mass at the back of Owen's head. We were so distraught the consultant had to stop every now and again to allow us to regain some composure. He was visibly affected and I have always felt immense gratitude that he seemed to really care.

In an instant everything was altered. The life we thought we had designed for ourselves disintegrated that Friday night.

It's a Dad's Life returns next week