ABOUT five weeks ago, my three-year-old son announced that he was a girl.

He took to wearing a hand towel, to look like long hair, draped over his head while tottering about in high-heeled shoes, carrying a handbag.

Although he didn't know the sex of the new baby we were expecting, he insisted it was a boy, while proudly pronouncing to anyone who would listen that he didn't have a willy any more. "I'm just going to do a wee-wee out of my bottom," he'd tell me on the way to the toilet.

My theory about his attempted sex-change is that he had somehow got it into his head a new baby girl in the family would be a cause for great celebration, while a boy would be a bit of a disappointment.

Why? Well, I should be used to it by now. After the births of my third and fourth sons, the isn't-it-time-you-had-a-girl comments came thick and fast: "Oh dear, never mind. Better luck next time," they said.

I had hardly recovered from the shock of discovering I was pregnant for the fifth time than they were at it again. "Hoping for a girl this time?" "No, not really." "Just keep telling yourself that and maybe you'll get one this time," they said sympathetically.

"Think pink, my daughter did that and it worked for her," I was told. By the fourth month, I was threatening to have a T-shirt printed with huge letters emblazoned across my bump: 'No, I'm not trying for a girl'.

Like most people, all I wished for was a healthy baby. I would have been delighted with a girl, and equally delighted with a boy. What I couldn't understand was the number of people for whom the value of having a child of a different sex seems so important.

Like the dozens of British couples queuing up to pay £15,000 in a Belgian clinic to choose the sex of their child, using a new 'sperm sorting' technique, some people appear to confuse having a baby with doing a spot of catalogue shopping.

It's an arrogant, self-centred approach, which reduces the child to a commodity. And why stop at the sex? Why not order one with blond hair and blue eyes, with an IQ of more than 140, an athletic build or a lively personality?

Some say they long for a girl so they can be more closely involved with her children, or they want a boy to carry on the family name. One grandmother, with three sons, once told me she wished she had had a girl: "someone to go shopping with".

Pity these poor daughters and sons if they don't turn out as planned and end up a constant source of disappointment. We don't own our children and it is unfair to project all our hopes and needs onto them.

Ever since I became a member of the exclusive Mother of Five Boys club, I have become used to people telling me I must be either brave or bonkers. But as I watched my four little blond boys, aged between three and eleven, beaming with excitement as they trooped into the maternity ward to see their new baby brother, I realised I am also incredibly lucky.

Holding the baby in my arms while they smothered him with hugs and kisses, I found myself brimming with pride. "He's really cool, mum," they said. The ultimate accolade.