Sharon Dempsey, whose son Owen died in 2004 following a brain tumour, is now pregnant again. In the first of a monthly column, she describes the pain and the joy of her pregnancy.

Sharon Dempsey's son, Owen, was diagnosed with an ependymoma brain tumour at the age of two.

He underwent nine hours of neurosurgery at the Heath University Hospital in Cardiff and 16 months of intensive chemotherapy at the Royal Hospital for Sick Children in Belfast. The tumour recurred and spread to Owen's spine when he was four. He then had further chemotherapy and radiotherapy. Owen died aged six on March 2nd, 2004.

Sharon is expecting her third child on July 11th.

The pink line indicates positive. I sit in Owen's room and cry. How can I be happy when my son is dead? My son has been dead less than two years and I am taking what feels like a huge risk, of loving another child and experiencing the highs and lows of parenthood for the third time.

In theory I want a third child. Desperately. In practice I can foresee the anguish of the birth, the painful memories that will engulf me with every milestone and the sad reality that this new child will never know Owen.

I phone my husband Liam. "Really?" he asks. He is astounded. We both assumed it would take a few months at least but for the third time we have hit the fertility jackpot straight away.

"Aren't you happy?" he asks.

"I don't know. I can't stop crying." The potent mixture of grief and pregnancy hormones reduces me to a blubbering wreck.

Recently we marked Owen's eighth birthday. We share a birthday and as he turned eight, I turned 36. It is his second birthday without us.

Birthdays hurt. I remember every one of his six birthdays here with us. Know what we did on the day, how we celebrated, what we gave him. Now all I can do is buy him flowers for the grave and a goat from Trócaire. We know he would love the goat.

His school has organised their second "mad hair" day to mark Owen's birthday. All the children arrive at school with crazy hairstyles and a donation for Clic Sargent, a cancer charity for children we came to know through Owen's illness. His sister Kate, in her last year of primary school, has her photo taken for the local newspaper, her hair as mad as the best of them.

From the graveyard where Owen is buried, Liam and I watch the children in the playground. The close proximity of the grave yard to the playground is a cruel comfort. We smile to greet many of the school's pupils as they visit Owen's grave to admire his flowers. Their dyed, spiked hairstyles looking comical as they stand respectfully quiet at his grave.

My brother has left a huge SpongeBob SquarePants made out of flowers. We laugh at the thought of older people visiting the graves not recognising SpongeBob and wondering what on earth this yellow creation is. We talk of the florist's skill at making such a great replica of a cartoon character.

After school we take Kate to the grave for her second time, our third, that day. She doesn't know about the pregnancy yet. I long to tell her, knowing she will be ecstatic. She misses Owen dreadfully and I hope another sibling will be a comfort to her on some level.

We want to wait for a few weeks before we tell anyone. This baby is our secret. We are not ready to share our news yet. There is a sense of shame and embarrassment that we should decide to have another child. It seems to be a betrayal, not of Owen but of our grief. It is as if others might interpret our news as an indication that we are "moving on".

I hate that phase. I could never move on from Owen and wouldn't want to. Our grief and pain remains, no matter what comes along in our lives.

I just know that a third child is waiting to be born to our family. No matter how distraught we are, I know we will cope. The thought of sleepless nights does not bother us. We have been through so many long, torturous nights watching Owen throwing up or dealing with agonising pain.

The reality of caring for a new born baby is not daunting. When you have cared for a sick child normal stress and strains don't compare. That doesn't stop us worrying though.

There are no guarantees that having experienced the worst imaginable trauma that I won't give birth to a disabled child. Perhaps I will experience a whole new range of problems. Owen was born perfect. No one knows what will unfold. The one thing I am sure of is that having a baby is not difficult, losing one is.