For my 40th birthday last November my husband bought me a giant silver helium balloon.

It clung to the ceiling in our kitchen for two weeks before we realised it had a puncture in the bottom.

On week three it started to wither away, slowly at first, almost imperceptibly. I would come in to make tea and watch it while the kettle boiled, noticing little other than it appeared slightly less fecund than it once had.

And then, one day, just like that, it was gone. Depleted. Nothing more than a crinkled crisp packet in the corner — a sad reminder of what once was.

The balloon now lives in a box in a small drawer in the attic of our home. A chapter closed but not forgotten. It is very much like another chapter of our lives that closed on my 40th birthday.

Cosmopolitan editor Farrah Storr reveals why she decided to not start a family with her husband (Blazer, £89.99 and trousers, £39.99, zara.com)

The chapter that began four years earlier when we decided to call time on trying for a family. Even if I changed my mind — and there were moments when I wondered if we had made the right decision — that door felt firmly locked now; my fertility (confirmed by numerous studies and no-nonsense doctors) almost all but depleted.

I didn't always know being a mother wasn't for me. Motherhood was something I just assumed would probably come my way. A bit like chin hairs. One day you are without them, the next, lo and behold! There they are.

When I thought about motherhood, I didn't crave holding a baby in my arms or dream of watching a mini me bend and plié on a dance floor. But I did imagine older children, who would one day blossom into friends and who would (hopefully) be there in my dotage. What I craved from motherhood then was not so much the idea of children, but the idea of a family. Family is what I have always known.

I grew up the third child of four in Salford, Manchester. Dad was the emblematic self-made Pakistani immigrant who had made good on a corner shop and went on to run a successful property business. Mum was a teacher with prospects.

There was almost 20 years' difference between my eldest sister and my youngest brother, which meant teenage upheavals lived side by side with toddler meltdowns throughout my childhood.

There was never any stillness in our home. TVs blared, tempers frayed and mum was an attendant nursemaid to whichever child's demands were greatest that day.

Farrah says that motherhood was something she just assumed would probably come her way (Dress, £69, phase-eight.com; shoes, £450, maxineshoes.com)

The concept of the 'juggling' mother is a cliché now, of course, but juggling was exactly what my mother did. I would watch her life from the sidelines — a circus act of spinning plates (children, career, friends, marriage).

The cracks in those plates manifested themselves throughout my life. Mum was always the last to pick my brother and I up from school. Her cakes for the school bake sale, made with haste and love at midnight, were always the last to sell. I witnessed her friends drift away, along with senior positions at the school where she worked, 'a sacrifice too far' I heard her lament to a nodding aunt.

As for her marriage to my father, I remember two people who appeared to speak only in raised voices. And yet mum epitomised 'having it all'. She was the Baby Booming incarnate of what life looked like if you took every opportunity that came your way.

She got the education. She married the man. She mountaineered the career ladder and produced a child almost every decade. And this was what it looked like. Success indeed, but a success dimmed by a thousand tiny sacrifices and clouded in tiredness.

Farrah, pictured with her husband William, decided around her 35th birthday they should start trying for a baby

Having it all, as demonstrated by my mother, reminded me of a Pointillist painting. Viewed from a distance it all looked so effortless. Up close its painful, painstaking effort was clear.

And she wasn't the only one — other women I knew would whisper almost shamefully about the struggle they felt. The rushing, stupefying exhaustion, constant micro-renegotiation of their lives: dinner with the husband or snuggle with the kids; weekend brunch with friends or playtime with the family.

And still, this was how I imagined my life would also be.

A few weeks shy of my 35th birthday and with one editorship on a national magazine, Women's Health, behind me, my husband and I decided now was the time to start a family. I had 'leaned in' to my career as far as I could, as had my husband, whose career as a writer was finally taking off.

After Farrah and her husband began to try for a baby, nothing happened. So they looked into IVF

We tried. Nothing. My husband would bring home the weekly shop and there among the tangerines and rice packets were fertility monitors and plastic pee sticks. They lived on our bathroom cabinet, a daily reminder that time was moving on.

Still nothing. I carted my womb off to Harley Street to see an acupuncturist known as 'the baby whisperer', whose waiting room was crammed with sad-eyed women flicking through baby magazines.

I knew everything about IVF — the needles, the drugs, the percentages, the cost, the fact that little purple track marks would live on your stomach like a snail's trail throughout the entire process, the painful bruises from constant injections. What I didn't know was how it would feel — for me, for my husband, for our marriage. No books had a language to explain that.

I lay on her bed, my eyes closed, as she popped a dozen different needles in my feet, hands and stomach. It felt like expensive voodoo to me, particularly when she sent me off with a list of hippy-ish sounding pills and a prescription for yoga and sex. I carried on regardless.

My husband did his part too — blood tests, samples, working out and taking himself off to bed at 10pm. All the things Google told him would bring child-enhancing sperm. We went for every medical test imaginable. Nothing. Except as one doctor told me: 'You are in great health!' We were the shiny new car, it appeared, that just wouldn't start. And so we prepared ourselves and our lives for IVF.

I knew everything about IVF — the needles, the drugs, the percentages, the cost, the fact that little purple track marks would live on your stomach like a snail's trail throughout the entire process, the painful bruises from constant injections. What I didn't know was how it would feel — for me, for my husband, for our marriage. No books had a language to explain that.

I listened to real women who had been there before me. Of the six women I knew who had gone through IVF, only four were successful. Of those, only one said their marriage had remained unchanged. It appeared you could approach IVF with as much academic rigour as it was possible to have, but you could never account for what the fallout might look like.

Farrah says she didn't know was how IVF would feel — for her and for her husband and for theri marriage

There was an added complication too: my husband had said, if we were successful, he would give up his career in order to support mine. I knew it was not what he wanted, but it was indeed the most sensible option as I was, at that point, the main breadwinner.

What's more, I had also just been offered my dream job as editor-in-chief of Cosmopolitan, a magazine I had tried my entire career to work on. By the time my turn came around to edit it, however, it came with enormous challenges: I had to get it back to being Britain's number one magazine. The hours were long. Most of the team resigned within the first few months. It required grit, resilience and every bit of energy I had.

Often my job is the last thing I think about before I go to bed at night, and the first thing I think about when I wake. That's what happens when you are lucky enough to find a career that fulfils you as much as you fulfil it.

To complicate things further, we had just decided to move to the country which meant a three-hour round commute and occasional nights staying over in London. But, bit by bit we got there turning Cosmo into the success we had been challenged to make it again.Yes there are lovely things that come with the editorship of a glossy magazine — the glass office, the glamorous parties (though I've never been one for a party, truth be told) and a good salary, but nothing beats waking up every day and marching into a job I love.

Often my job is the last thing I think about before I go to bed at night, and the first thing I think about when I wake. That's what happens when you are lucky enough to find a career that fulfils you as much as you fulfil it.

But as I lay there at night another thing struck me . . . that despite editing the very magazine whose crusading mantra through the Sixties and Seventies had been that women could 'have it all', I wasn't sure I could do it all. Or, even wanted to have it all.

It was a warm spring afternoon in late April 2017 when I made the 55- minute journey to the IVF clinic. As the doctor, a Greek woman with warm, sympathetic eyes, scribbled lists of the different drugs I would need and the addresses of clinics in Kent I could visit, everything became muddled.

When Farrah saw a doctor about IVF treatment 'everything became muddled' and she realised she perhaps didn't want children

Her words started to swim around me. It felt as though I was watching a movie of someone else's life, the life of a woman who would do anything to have a child. That woman was not me. It had never been me. I had never had the ovarian ache some women spoke about through watery eyes. I didn't have children's names planned. I didn't choose the house we lived in because of its school catchment area.

I willed myself towards a destination called 'motherhood' without thinking of how hard the journey to get there would be. And if I didn't want it enough, if I wasn't sure I could do it well enough on top of everything else I had in my life (my career, my marriage, my desire to see the world) then was it worth it? I took the doctor's scribbled notes, put them in my handbag and drove home.

That night, as my husband and I sat watching TV, I leaned against his arm, looked up at him and said: 'I'm not sure I want to start a family.' He looked at me, kissed me on the forehead and replied. 'I'm so glad you've said that because neither am I.' It was that simple. And yet it was not simple for those around us.

That night, as my husband and I sat watching TV, I leaned against his arm, looked up at him and said: 'I'm not sure I want to start a family.' He looked at me, kissed me on the forehead and replied. 'I'm so glad you've said that because neither am I.'

In the early days, once we had told those close to us, their denial at our decision was by turns, amusing, annoying and occasionally offensive. Close friends would lament what a shame it was because we would make such good parents.

Acquaintances meanwhile would band about the phrase 'missing out' as though we had decided not to join them to see Coldplay in concert. At work functions conversations would falter when I was asked if I had children, and my desire to make dining companions feel more at ease was to regale the entire story behind that decision.

Cultural coercion, meanwhile, asserted itself through well-meaning phrases such as: 'Well, you still have time if you change your mind.' And changing our mind was always there, I suppose. After we made our decision not to pursue IVF, it is intriguing that we didn't start using contraception, for example (though we did skip sex around my alleged 'fertile' period), and I kept a coral cashmere baby's blanket at the top of my wardrobe.

About 18 months after that brief conversation my husband even came home one night and regaled me with the scene of a reuniting father and daughter he'd witnessed through his train window. When they hugged, he said, it almost brought him to tears.

Turning 40, no matter what the quacks say and how many anecdotes you hear of women finding themselves pregnant (naturally!) at 48, is the end of the road for most of us. By the age of 30, research shows an average woman has just 12 per cent — barely an eighth — of the eggs with which she was born. By 40, only 3 per cent of the two million or so original eggs remain.

Farrah, pictured with Rebel Wilson at the Women of the Year awards, eventually told her husband she didn't want to have children

You can, of course, throw money, time, science and true dedication at the issue. But the reality is your natural fertility has all but ebbed away, which means conversations about 'changing your mind' ebb away too. If there was ambivalence about remaining childfree in my late 30s, there is now a finality to it. But with that comes relief at being released from a ticking clock that has dogged me for a decade.

Of course my husband and I talk about our childfree existence all the time. To not talk about it would be odd, because whether we like it or not, it does define us and the lives we now lead.

We have had to readjust the lives we thought we were going to lead, into the lives we now have. 'Spare' bedrooms have been converted into offices and dressing rooms; two giant dogs have become the recipients of our affection.

We have made peace with the fact friends our age with young families are too busy to see us. Being childfree makes you incredibly well organised, planning as you must for a future without dependants.

Farrah says her husband and herself talk about their child-free existence 'all the time'

I have tried to plug gaps where there was once a child-shaped hole. My weekends are now given over to gardening, while I make sure I do the things not having children has freed up my time to do — travel, write a book, volunteer.

While there is no doubt the notion of 'having it all' is vital to raise aspirations and broaden the ambition horizon for many women, it is also vital to have the option to say 'no' to wanting to have it all too. After all the founding principle of feminists is having the choice to do what you want.

I didn't want it all. Neither do many young women I know. For some of you that may be confusing. For me it is liberating. Because the assumption is that if you can have everything, then why wouldn't you? But for me, having it all-ish is good enough.