The singleton is no more. Bridget Jones has married Mark Darcy, Carrie Bradshaw has nailed Big and Ross and Rachel are finally together for ever, bringing to a close a decade of singleton sagas which have defined Anglo-American cultural life for a particular generation of women. In one advert break, the schedules have leapt from lack-of-boyfriend angst (Friends, Sex in the City) to husband tedium (Desperate Housewives) without a thought for those left behind.

These are the late-thirty and early- fortysomething women who didn’t get their man and are facing life’s next hurdle — having children — alone. There is a large tranche of single women who, after years of agonising, have resorted to taking control of their biological destinies by opting to become single mothers, so overpowering is their maternal urge. We are the latest social phenomenon, post-panicky-Bridget, pre-menopausal-Germaine, gagging for a gurgling sprog and going to extraordinary lengths, physically, scientifically and financially, to get pregnant. We even have our own acronym, Sadfabs: single and desperate for a baby. Our biological clocks have been shrieking for a decade and we’re almost out of time. We’re also alone, which makes things problematical.

We will all have our different reasons for finding ourselves alone in the declining years of our fertility, and doubtless we’ll be going about the business of trying to conceive in different ways, but the one thing that unites all of us reluctant Sadfabs is that we’ve forced ourselves to face the gritty possibility of a life without children — and rejected it out of hand.

Rejected it after years of worry, of monitoring our menstrual cycles, of anguished debate with family and friends, of reading every IVF triumph and tragedy in the media, of fearful financial calculation. And could we really manage alone? How would we cope with work and childcare, how would we explain our actions to our offspring, what happens if we get ill or incapacitated, what the hell do we write on the birth certificates? Concluding that love will get us through it because, well, it’ll just have to. Selfish? Irresponsible? Mad? Er, no — just maternal.

And don’t underestimate that urge. This is my third time of trying IVF. After writing this, I’ll be peeing on a £19.99 stick to gauge whether I’ve ovulated or not. Five days after ovulation occurs, I’ll take myself off to a hospital in Chelsea (congestion charge £5; parking £3). I will open my legs to one of several doctors who have become intimately acquainted with my genitalia over the past 18 months, and have two thawed-from-frozen embryos, left over from my second cycle of IVF (£8,000, thank you), inserted into my 39½-year-old womb via a thread-like catheter, whose ascent into my interior will be monitored on a screen by all present until their safe landing is signalled by a flash of light and confirmation from the embryologist that the catheter is now empty, before handing over a cheque for £1,000 for the pleasure.

In my quest for conception I’ve swallowed pills, injected myself with hormones, fought nausea, undergone anaesthetic to have chemically harvested eggs clustering around my ovaries collected via vaginal puncture, waited, prayed, drunk disgusting Chinese herbs, had acupuncture, sweated, bled, cried, written cheques, and started all over again. I’ve spent £16,000, driven hundreds of miles, held down a job, been jogging, slept fitfully, eaten organic, abstained from alcohol and caffeine, monitored my vitamin intake, OD’d on chocolate (well, a girl’s gotta live) and slept alone.

Like every woman in the waiting room of the assisted conception unit at my hospital, I’ve sat silent, pale-faced and tense; unlike almost every woman there, however, I go home alone, unsupported by a blokey arm around my shoulders, to wait and pray, and count the 14 long days on my own. Baby-making in the 21st century for women of a certain age who didn’t get married, or partnered, goes like this: it’s just you, the Petri dish and prayer (oh, and your chequebook, of course). Making the decision to go it alone is a terrifying and daunting prospect, usually the result of years of self-scrutiny and projection, weighing up the potential pitfalls against the perceived pleasures. It takes bottle to go it alone; actually, it takes balls . . .

None of the options is particularly appealing if biological childbirth is the goal. It’s either a loving friend, a sperm bank or a one-in-a- million chance on a one-night stand, assuming you have nabbed the geezer during the critical 48 hours post-ovulation. All the routes carry risk, and all run through an emotional, moral and ethical minefield.

Conceiving is an uphill struggle due to our advanced age, and staying pregnant a challenge, bearing in mind that 40 per cent of all pregnancies to women over 40 end in miscarriage, and then there’s the increased risk of carrying a Down’s syndrome baby. For some, the costs alone are prohibitive. Sadfabs remortgage homes, forgo holidays, take up evening jobs, and still find time to study family law and the Human Fertilisation and Embryology Authority guidelines, as well as the minutiae of their reproductive systems. Making the decision, understanding the law, identifying the sperm donor, and signing up for the whole messy business is just the start of a long, expensive, emotional and physical journey, with no guaranteed happy ending and distressing pitfalls littering the path.

I figure I’m one of the luckier ones. I’m the right side of 40 (just), I’ve been pregnant before (wrong time, wrong man, faulty contraception) and I have a close, single, male friend happy to donate sperm and to be the legal father of my child, recognised as such and involved in our lives. But there’s no doubting the complexity of the single-parent lifestyle. You’d have to be one nappy short of the jumbo Huggies pack not to be aware of the practical impossibility of juggling the roles of breadwinner, housekeeper, cleaner, shopper, cook, nurse, chauffeur, counsellor, DIY expert and mum.

Every day the scary scale of practicalities threatens my resolve: I’m a freelance journalist, working haphazardly and to deadlines. How am I going to cope when I’m the only one doing the night feeds; what happens when the sprog falls ill and I’m at work; how will I answer the phone when I’m cleaning up sick, removing spaghetti from the ceiling and changing the Babygro for the fourteenth time that day? When will I sleep, shower, get to Waitrose and find a husband? I’ll just have to manage, the way that women have always done. Women have brought up children and run homes on their own throughout history, be it through spousal loss, poverty, disease or war. Most of them are tough, resourceful, full of love and, with luck, have a network of friends and family near by.

For myself, I’ll continue to inject hormones, swallow drugs, hurl money at private institutions, imbibe oriental potions, chant, stand on my head and do whatever it takes to nourish the life I want to grow inside me. I’ll find ways to care forany children I’m lucky enough to produce. And I’ll love them enough for twenty, let alone two, because the thought of living without children is unendurable to me.

Maternal instinct is a powerful drive. Being a single mum is not what I wanted to be. But being nobody’s mum isn’t an option. And it’s now or never. All eyes on that Petri dish.