At the age of 32, Marisa Knowles, a medical sales representative, felt her life was progressing just as she'd always planned. For three years, she had enjoyed a happy, loving relationship with her partner, 35-year-old Matthew Henry, even if he had seemed a little distant lately. Once they had saved enough for a deposit, they'd buy a house, get married and settle into the cosy domesticity she envied in so many of their friends.

But one evening two years ago, that picture-perfect future fell apart. Matthew, an IT specialist, came home late with the smell of alcohol on his breath, and an argument ensued. He was being frustratingly evasive. "Matt, what's your problem?" yelled Marisa.

"I don't know how to do this without hurting you, but I, I ..." he stammered.

She knew what he was going to say even before he'd finished the sentence.

"I love you, Marisa, but I don't think I'm in love with you anymore," he confessed, fat tears rolling down his cheeks. "I don't want the same things as you - I don't want to settle down, get a mortgage and have kids. It's just not me. I don't know if I'll ever want it."

Like increasing numbers of women in Australia, Marisa had suddenly found herself single, contemplating a life very different to the one she'd planned. With that confession from the man she loved, Marisa joined the ranks of the "nearly-weds", those of us who've spent years in long-term relationships that we thought would lead to marriage, but haven't.

For many women, the shock of finding themselves single, at a time when they thought they would be planning their honeymoon, can be devastating, particularly when everyone else in their peer group seems to be happily married. It comes as some surprise, then, to discover that, statistically, a lot of other women are in the same boat - the latest census figures (from 2006) reveal that 35 per cent of women aged 30-34 are single, as are 31 per cent of women aged 35-39.

You might think that this sizeable cohort of independent, empowered, single women might have seen off traditional ideas of "spinsterhood", which saw single women pitied and ridiculed. But Sex And The City aside, the negativity surrounding singledom remains. In fact, going solo has become less desirable than ever before.

Firstly, there's the much-discussed biological imperative: that a woman's fertility drops dramatically after she turns 35 (a fact we're reminded of almost daily in sensationalist newspaper reports), which places enormous pressure on the search to find a partner. Then there's the way that single women are portrayed: as clueless, Bridget Jones-types (even the Sex And The City girls are depressingly frivolous at times) or sperm-hunting "cougars", a term loaded with misogyny. And there is women's own sense of failure; they may have career success and financial independence, but a stable relationship remains elusive, which leaves them feeling there must be something intrinsically wrong with them.

"There's a stigma attached to 'spinsterhood' that hasn't been eradicated," says Dr Rebecca Huntley, director of research firm Ipsos Australia. "There's a sense that a woman is alone through her own fault."

That's how 38-year-old Kate Reilly, a nurse from Melbourne, felt when her partner walked out four years ago. "The despair was overwhelming," she confesses. "I remember sitting in my car, loaded up with all my belongings, howling like a two year old at the thought of going through the whole process of trying to meet someone again. Now, I was in my mid-30s. There was this massive sense of loss and anger, and with that came a feeling that I just wasn't good enough. Was there something wrong with me? How come everyone else could hold on to a relationship and I couldn't?"

Marisa's break-up triggered the same bout of introspection, coupled with a sharp sense of betrayal. "In the early days, Matt would say what a great team we were and talk of our future children, so I assumed it was the natural order of events," she recalls. "I was wrong. Now, I feel like I wasted three years of my life with a man I'm not sure I ever knew. I'm still getting over the anger two years later, while he's still playing the field."

Of course, men can afford to "play the field" for longer because their fertility doesn't decline at quite the same rate (although several studies have shown the quality of sperm deteriorates significantly post-40). In her research, Dr Huntley identifies "40 as the new 30" for men, meaning they often don't feel the urge to settle down until their fifth decade. Brad Pitt is a prime example, she adds, in that he didn't appear inclined to have children before turning 40 - then promptly landed himself a "rainbow family" of six.

"For women, 30 is the 'magic' number," she says. "We spend our 20s having fun, furthering our careers, and then view our 30s as the time to get serious and have kids. But even if you're living with a partner, you might find at 30 that your partner is 10 years away from committing, which can come as a shock."

But is finding yourself single at 30 really as bad as it seems? The reason that women of our mothers' generation were married at that age was simple: it was the easiest and most socially acceptable way to leave home, travel and have sex. The flip side was that many married the first man they fell for - and were stuck in that starter relationship for the rest of their lives. Perhaps it's better to be single in your 30s, after travelling and experimenting, than being stuck with your first proper boyfriend, adds Dr Huntley.

What's more, women in their 30s are often much clearer about what they want - or don't want - in a partner, meaning they "meet, mate and multiply" quickly when they do find one. "Now a subset of the generation that has put off marriage is changing the way they make families," wrote Rachel Lehmann-Haupt in New York magazine recently. "Anxious not to miss out on domestic life, they are speeding into life's next act in less than two years; sometimes in just a few months."

I left a seven-year relationship in my mid-30s. It had become stagnant, so I moved on, despite it being the scariest decision I ever made. Most of my friends were married and pushing out babies, while I was on my own at 36.

The feeling I was somehow missing out was most acute on those lonely Sunday mornings when I'd call up my friend, only to find her enjoying brunch with her in-laws, the sound of children in the background. As many newly single women discover, there's also an expectation that single friends will fit in with the family's arrangements. "If I want to see my girlfriends who have children, I have to go to them," says one newly single 30-something from Melbourne. "After splitting with my boyfriend in January, I find myself spending every Saturday driving from one suburb to another to see friends who hold court with their kids at home."

Advertising executive Michaela Noonan*, 35, who emerged from a five-year relationship in February this year, admits to being guilty of prioritising her partner over her friends. "I'd meet up for a quick coffee with them, but if I was asked to go for a drink on Friday night I'd refuse, as my partner came first."

Now, it's Michaela who's being scheduled in for a quick latte by her coupled-up friends. "It's not that they've excluded me," she says. "It's just that our lives have become very different. I was invited to a dinner party recently and the couples sat facing one another while I was at the end of the table."

"The problem for people in couples is that they often can't remember what it's like to be single," cautions relationships expert Dr Gabrielle Morrissey. "That's where the 'smug married' stereo-type comes from, in that couples lack empathy as they believe they won't ever have to experience singledom again."

Interestingly, Dr Huntley believes society in general places more value on the relationships of married women than those who are single.

"The common complaint of single women is that their family relationships - with parents, cousins and friends - aren't seen as being as important as those of women who have a husband and children. We have a very narrow view of what constitutes family life."

Let's not forget, too, that there's a certain amount of luck in meeting a lifelong partner. "We overlook the fact that fate plays a big part in our relationships," adds Dr Huntley. "There are wonderful women out there who simply haven't found a suitable partner."

After the initial shock, I came to see singledom as a period of growth. If I wasn't single, would I have written my novel? Or had relationships with some incredible and not-so-incredible men, who helped me understand myself better and what I wanted from a relationship?

Time has also given Marisa a fresh perspective on her relationship with Matt. "Looking back, I can see there was a level of co-dependence, in that my life revolved around him," she says. "Being single has given me a chance to focus on myself. I've started to learn French and plan to travel to France next June. If I can't convince a girlfriend to come, I'll go alone - that's how far I've come."

Being single is a time to truly understand yourself, says Dr Morrissey. "It isn't just about meeting somebody else, but an opportunity to really enjoy your own life. You learn to challenge yourself, to grow. It's a special experience and one you can't have inside a couple. This is an opportunity to focus on yourself from a mature standpoint, which can only make for a healthier, more secure relationship the next time around."

*Names have been changed

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