Kasey Edwards had only gone for a routine smear test, but her gynaecologist offered to check her ovaries while she was there. One turned out to be polycystic – it was producing eggs that were faulty. The other was riddled with endometriosis. On top of that, her fallopian tubes were blocked. In terms of fertility, this was bad news: the doctor told Edwards she had only 12 months to conceive.

It was a huge shock. Edwards was 32. She liked her life as it was. "I've never been maternal. I didn't grow up wanting to be a mummy. The whole idea of motherhood seemed like a bad deal. Why would anyone do it?" A management consultant, she had seen what having a baby did to the careers of her colleagues. "And you don't have to Google very long to find out what it does to marriage and mental health."

She had been with her boyfriend, Chris, for less than a year. Only two weeks before seeing the doctor they had agreed not to discuss babies unless they were still together a year later.

But it was now or never. When her boyfriend arrived home from work that evening, she asked, "Can you love a barren woman?" He listened to her "talk in circles for a couple of hours" trying to come to a decision and then announced that he knew what to do: he wanted a baby. "What, just like that?" Yes, he replied. But because of his Catholic upbringing, he had a condition: it must be a natural conception – no IVF.

After trying naturally, Edwards found herself thinking: "Six months of trying and six months of failing. Perhaps I'm already infertile." At her next appointment, the doctor was blunt: "Six months ago you had one and a half ovaries. Now you've only got one. How much longer are you going to wait before you start IVF?" Chris broke and consented to IVF. They had at most a few months left, with poor-quality eggs. Edwards was at her lowest: "I really felt a failure. I cried every time I went to the IVF clinic because it felt like it wasn't the way it was supposed to be. I looked around when I was having the embryo implanted, and I thought, there are five people present for the conception of my child and three of them are wearing surgical masks. It's not the stuff of fairytales."

Violet was born 18 months ago. Chris, 38, is now her husband. They live in Melbourne, Australia but I meet Edwards for coffee in London, where she is promoting a book about her experiences. The book – 30-Something and the Clock is Ticking – has been written to help other women decide whether they want a baby at all and how soon they need to do something about it. But is Edwards really in a position to teach anybody? She only changed her mind about motherhood because her body gave her a sudden, early ultimatum; others, more fortunate with their health, may not feel that her experience holds a lesson for them.

In fact, her story is not unusual. There is a lot of noise around at the moment about giving women a "wake-up call". Earlier this year a study by the Royal College of Obstetricians and Gynaecologists (RCOG) warned couples against waiting. It emphasised that for women aged 35, fertility problems are six times more common than at 25. By the age of 40 a woman is "more likely to have a miscarriage than give birth". Up to 30% of 35-year-olds take a year to get pregnant, compared with 5% of 25-year-olds.

This is brutal news if you're in your 30s – or older – and haven't found a long-term partner. Or if you've just broken up with someone with whom you hoped to have children. But obstetricians and fertility experts can now increasingly be drawn on the optimum age to have a baby. Dr Tony Falconer, president of the RCOG, now says "between 20 and 35." (Dr Miriam Stoppard has said, hilariously, or perhaps not so hilariously, "Physiologically, the best age is 15".)

Of course, there is no such thing as the right age. But the point is, all the statistics point to a conundrum for young women. Despite all the advances in technology and the workplace, that ticking clock is still there and if you don't have its existence at the back of your mind, you may miss the chance to have a family.

The IVF expert Dr Gedis Grudzinskas says it's more difficult after the age of 27: "When women have got used to having a lot of freedom to run their lives as they wish, they do not want to hear that they may not be able to conceive. They perhaps need to compromise, find Mr Good Enough and have a family earlier."

With the benefit of hindsight – and having had the good fortune to have a man in tow at the time – Edwards agrees. "I think it's partly our own fault. We don't start our search soon enough. We get to 35 and think, better start looking around for a father. That will take six months at least. Then maybe 18 months to two years before you can bring up the baby subject. And before you know it you're 40 and have a 5% chance of having a baby."

While accepting that her own condition was unusual, she still feels there's a message for Everywoman. "It was a big hit to how I saw my relationship with the world. A lot of women don't understand how fragile their fertility is because they don't want to hear it. People always say to me, 'I know someone who had a baby at 39.' But I sat in IVF clinics with women who had been trying for years, and many of them were not going to get babies at the end of it."

Unwelcome though it may be, her analysis of the medical picture is broadly accurate. A 30-year-old woman stands a 22% chance of getting pregnant in any given month. By 35, that drops to 18%. By 40, it's 5%. By 45 you're down to 1%. By 25, women have lost 80% of the eggs they were born with. By 35 that has dropped to a 95% loss. (Maybe Miriam Stoppard was right after all.)

One reason women are willing to gamble over their fertility is that many are not even sure they want a baby at all. This is a bigger issue in Edwards's native Australia, where parental leave has only just been introduced. Edwards lost her job when she was pregnant, as did half of her mothers' group.

A lot of mothers she interviewed admitted regretting having children. "They said they preferred their lives before. It is such a huge sacrifice and it changes your life so much. There is a difference between loving your kids and loving the lifestyle that motherhood imposes. How could you possibly love cleaning up poo and vomit 24 hours a day? Can you love just being a mother? Not being promoted at work? Earning less money? I really struggle with the idea of being on duty all the time. I didn't realise that about motherhood."

Edwards has two more embryos in the freezer but is not sure she wants another child. "I noticed that all the women I spoke to who said they wished they didn't have kids had more than one. Is that the tipping point? Is that when it all becomes too hard and it's not worth it?"

Maybe this is a shift, Edwards implies, towards more women choosing to be child-free, or choosing younger motherhood. We often forget that having a first child over the age of 35 is a relatively recent social trend.

The number of mothers giving birth after their 40th birthday has trebled in the last 20 years: 27,000 babies born to mothers over 40 last year compared with 9,336 in 1989. We now think of "older motherhood" as mid- to late-40s, maybe even later.

The "ticking clock" dominated the cultural conversation for a while a decade ago when Sylvia Ann Hewlett's Baby Hunger: The New Battle for Motherhood came out. Baby Hunger carried many of the same messages as Edwards: "Don't delay, you'll regret it." It created a media firestorm in the US, but the book didn't sell. Women didn't want to read about the babies they wouldn't have. In this country, Kate Figes wrote in May 2002 that it was "another polemic, telling what we already know". Figes quoted a local bookshop manager, who said: "If women want to get pregnant in their 30s it's much too scary and depressing to read something that says they might not achieve it. It's a mission for them to get pregnant, so they buy technical, practical books on infertility."

Then the mood moved on. There was a backlash and Hewlett's warnings were seen as scaremongering. Stories about advances in egg freezing and "Bridget Jones babies" became popular, peddling the idea that if you froze your eggs in your 20s you could wait as long as you like. (That technology, if it will ever exist, is still light years away.)

Positive-thinking books such as Elizabeth Gregory's Ready: Why Women Are Embracing the New Later Motherhood became popular, with chapter titles such as Fifty is the New Thirty.

Now with Edwards's "now or never" mantra we've come full circle. There is even an alarm clock on a woman's stomach on the front cover. The book is cleverly marketed, and it's a fun read. But I can't help wondering if Edwards is asking the impossible: for other women to make themselves face a decision that she only faced because her gynaecologist forced her to. "When I found out, I felt really angry. A bit like a spoilt brat. It was the first time in my life that I couldn't do what I wanted. We grow up thinking our life is full of endless opportunities and possibilities."

Her message is that life isn't. But don't we all have to discover that for ourselves?

Thirtysomething and the Clock is Ticking: What Happens When You Can No Longer Ignore the Baby Issue (Mainstream, £7.99). To order a copy for £6.39 with free UK p&p, go to theguardian.com/bookshop or call 0330 333 6846