At first, I was appalled by the idea. “We won’t be doing that!” I said scornfully when the fertility consultant suggested IVF using a stranger’s eggs. “What would be the point?”

“You would be carrying your partner’s child,” he replied, “forming strong bonds during pregnancy and giving birth to your baby.”

I shook my head. “No, it’s not for me. Anyway, I still have faith in my own body.”

He gave me an odd look. Hadn’t I been concentrating when he showed me the difference between a 30- and a 40-year-old’s ovum on his computer screen? One resembled a bright, shiny, Saturn-like planet and the other a blurry blob. Well, no, I hadn’t, because I was suffering from the apparently common delusion that I was younger, fitter and more fertile than virtually anyone else of my age.

“Good luck,” he said, shaking my hand. “At 44, you’ve got around a 1% chance of conceiving per cycle. I hope it works out for you.”

His nonchalance made me seethe. “Oocyte donation? It’s so bizarre!” I railed at my partner, Richard, back at home. “I bet he was just trying to get more money out of us.”

A couple of days later, an ex-colleague rang and mentioned that she was going through the adoption screening process, after trying to get pregnant naturally, then by regular IVF and finally using her younger sister’s eggs.

“Your sister’s eggs? Isn’t that incestuous?” What a repulsive idea, I thought.

The problem was, I didn’t understand what it meant to long for a baby. Until I met Richard, a month before my 42nd birthday, I had assumed I wouldn’t be having one. Being a mother had always spelt drudgery to me. I probably could have gone for it sometime in my 30s, but didn’t have enough trust in my partners at the time. I wasn’t ready and I hadn’t met the right person.

With Richard, though, I could visualise sharing the joy and hardship of child-rearing; I could see that parenthood would work as a partnership for us. I also loved him absolutely and he was desperate to be a dad.

Spurred by my love for him, something new started to drive me – the “biological urge” that people talk about. But it still wasn’t particularly strong. When we conceived the very first time we tried, I was pleased, but I couldn’t help worrying about the future, about money and about how I would cope without sleep. Then I miscarried, at nine weeks.

At the hospital the day after I started bleeding, I had a scan and saw a foetal heartbeat on the monitor. Seven days later, there was nothing there except an empty sac that looked like a punctured balloon. Suddenly everything changed for me. An obsessive desire for a child engulfed me like a fog. It was seeing that little pulsing heartbeat, I think. It haunted me like a distress signal. I felt that somehow I should have done more to save it.

I comforted myself with the thought that it would be easy to conceive again. However, after another miscarriage six months later, nothing happened. I had tests and tried assisted conception; we went on holiday to “relax”. I hurtled past my 45th birthday. We got engaged: a welcome distraction.

It was time to face up to the fact that my chances of achieving a full-term pregnancy with my own eggs were minimal. By now I had for months been mulling over the idea of using a donor’s eggs, pushing, pulling and probing it, trying to come to terms with it. I had heard of several instances of women within my wider group of acquaintances getting pregnant that way. Friends quite casually mentioned people they knew who had conceived using another woman’s eggs. No one remarked that it seemed odd or unnatural. Instead, they agreed that if it was a choice between that and remaining childless, they wouldn’t hesitate.

What was my problem, then? Was it ego? There were particular family attributes I felt I wanted to pass on in my genes, inherited assets that were evident in my nieces, that I didn’t want a child of mine to miss out on. I also wondered whether I would be able to bond properly with a child who lacked any family resemblance. Would I recognise him or her as mine? Never having felt particularly maternal, I wondered if I would need that sense of heredity to relate to my son or daughter.

I couldn’t help remembering the countless times I had sized up an infant and said, “He’s got your eyes!” or, “Doesn’t she look like her dad?” Using another woman’s eggs would rule out the possibility of spotting my brother’s dimples in my child, or my granny’s way with a sewing machine. I pictured friends and relatives walking on eggshells when it came to discussing familial resemblance, or putting their foot in it, or just trying to be kind. “It’s funny, she looks just like you, even though she’s, you know, not, er...”

Genealogy was also an element: I’ve always relished hearing about what my grandparents did in the war and looking at grainy photographs of my great-grandparents. How would donor egg kids feel about their antecedents if they weren’t blood-related to them?

“Do we need to tell them?” Richard asked. We decided it would be wrong to keep it a secret. How could we teach them to be honest if we were deceiving them? Kids have a sixth sense for that kind of thing, anyway.

Of course, they would always be able to trace their forebears on Richard’s side, but that wouldn’t involve me and all my wonderful tales, not least the one about great-uncle Charles who went to the bank and never came back. Naturally Richard’s relatives didn’t seem as interesting as mine, or at least his parents were less than forthcoming about their scandals and skeletons. Would we be a proper family without an anecdotally laden family tree?

I don’t know why I was being so obtuse. None of these concerns has ever troubled my sister and her gorgeous adopted sons, as far as I know. What’s more, the parent I most loved and from whom I received the most care and affection in my life was my now deceased stepmother, with whom I shared not a chromosome, gene or blood cell. From the moment she met my dad, this amazing woman made me and my siblings feel every bit as loved as her own children, and in doing so she taught me how to do the same. How could I think I couldn’t cherish a donor egg baby? It was an insult to my stepmother’s memory.

Yet, having decided to take the donor route, I still found myself searching for connections that would link me in some special way to the egg I would be nurturing. It was a romantic kind of obstinacy, and for a while I couldn’t shake it. I began to invent a mythology that tied the notional egg and me together.

The loss of donor anonymity in the UK, in 2005, had resulted in a shortage of sperm and egg donations, and an increasing number of Britons had begun to seek fertility treatment abroad. Richard and I had been told on good authority that Spain was at the forefront of embryo transfer by oocyte donation, and because I was born in Spain, albeit to English parents, and people were always saying I looked Spanish, this suited my flight of fancy.

I wondered about the Spanish woman who would become my egg donor. A British fertility consultant told me that people in Spain are culturally more altruistic than those in the UK; they have a much higher incidence of sperm, egg and organ donation. But becoming an egg donor is primarily a financially driven act, albeit a compassionate one, and I worried about poverty-stricken women doing it less out of choice than to put food on the table.

We decided, after some research, that we would seek our treatment at a clinic in Alicante in southern Spain. I knew nothing of Alicante, except that it was the setting for a story my father had once told me. Back in the 60s, he had travelled there on business. One afternoon, sitting in a semi-basement meeting room watching passersby on the street through windows high in the wall, he’d caught sight of a breathtakingly beautiful woman, her waist-length black hair swinging behind her. On a whim, he made excuses to his colleagues and rushed out to find her.

When trying to pick up a woman on the street in those long-gone days under Franco, the drill was to pursue her uttering outlandish compliments, relentlessly pleading with her to stop and speak to you. It seems Dad was rather adept at this custom, despite being married with children. He followed her for a good 20 minutes, until she eventually turned to face him. They met for coffee a few times before she guessed his marital status and dropped him, but he has never forgotten her beauty, her glossy hair and the shy smile she gave him at the end of his determined pursuit.

Clickety-clackety went the shuttle of my mental loom as I recalled this dubious tale. What if the woman was coincidentally the grandmother of the donor of my eggs? I liked the idea. It was a connection. I also understood that it was totally bonkers and kept it to myself.

The upside of this foolishness was that I stopped fretting about passing on my genes to my child and developed a preference for my fantasy alliances over my real relations. Yes, we’re quite a clever, arty bunch, I reflected, but addiction and mental illness are also rife among us. Of course, who knew what kind of family the donor of my eggs could be descended from, but it was a comfort to think that a child of mine just might be better off without my genes.

Looks were a concern, however. After all, it’s been proved that life is easier if you’re attractive, and I wanted the best for my child. But whereas – rather sickeningly – in America you can choose your donor by watching a video of her, and I believe you pay extra for prettier and better-educated women’s eggs, in Europe you’re not supposed to care about such things. Current health of the donor and family medical history are the important factors – and rightly so.

Yet I still tried to find a sneaky way of ensuring a better-looking donor. It wouldn’t be unreasonable to request that she have good teeth, would it? On health grounds, of course. I felt uncomfortable about it, because it was somehow an echo of 19th-century slave market inspections, but I asked all the same. Looking back, I think it was just a way of trying to exert some control over the process, and despite the clinic’s assurances, I bet they didn’t take a blind bit of notice.

Richard and I went to Alicante for a preliminary meeting. Our visit coincided with a big street parade, where marching brass bands played tunes that brought back in vivid flashes my early years of living in Spain. Everything fitted! I felt spiritually linked; this was meant to be. So it barely mattered that our chosen clinic made a less than favourable impression: our interpreter was like an automaton; the consultant kept stroking my arm; we were given a muddled explanation of the procedure; and the patient liaison popped her head round the door to watch me having an internal examination, quite unnecessarily.

Back home, I spoke to a friend of a friend who had been successfully treated in the Czech Republic at an oversubscribed fertility clinic with a 10-month waiting list. She had no special reason for going to eastern Europe, she said, except the clinic had a great reputation, achieved excellent results and struck her as having high professional standards. What’s more, the fee for her treatment had been half of what Richard and I were forking out. Faint alarm bells rang in my head, but I kept the faith in my Spanish connection.

In Alicante for a second time, again less than impressed by the protocol of our chosen clinic, I finally underwent an embryo transfer. Two weeks later, my pregnancy test came out negative and my fantasy bubble burst. Within a matter of seconds, all that crap about making links and creating meanings around the donated egg and donor went out of the window. I simply wanted to go somewhere I’d be in safe, professional hands and get the result I wanted.

I wrote an impassioned email to the director of the clinic in the Czech Republic. Because of my age, he agreed to give me a cancellation and treat me before Christmas. When he emailed the details of a potential donor – something the clinic in Alicante had failed to do – I didn’t care a jot that she was blond with blue eyes, my polar opposite in appearance. I expect I could have gone back and asked for more of a physical match, but all that mattered to me was that she was the same height and weight, 19 years old and in great health. It wasn’t just that I was desperate and didn’t want to seem fussy; I’d got over myself. (Although when I heard that she was a non-smoker, I couldn’t help hoping she wasn’t too much of a goody-goody.)

A close friend of Richard’s volunteered her eggs. It was an incredibly kind and generous offer, but I much preferred the idea of an anonymous donor. I sensed I would feel uncomfortable having a friend around a child produced from her eggs. There just might be an ownership issue there, if only in my imagination.

I met up with the woman who had received treatment at the Czech clinic and went on to give birth to “a magical baby son”. I didn’t like to ask how it felt to be pregnant with another woman’s eggs, but she reassured me all the same. She already had a five-year-old child, conceived naturally, and this pregnancy felt no different, she said. She also mentioned that a director friend had made a documentary about oocyte donation and discovered that there was evidence of chromosomal crossover between mother and foetus. It made sense, considering the shared blood supply, and I was very happy to hear it.

We discussed how people had reacted to the idea of her donor-egg baby. Her friends were all over the moon for her, she said. Her in-laws were initially confused, and inquired politely whether it meant she was a surrogate mother. Someone’s drunken neighbour had rudely asked her at the pub, “What’s it like to have another woman’s DNA inside you?” and, “Has the hospital told you when to break it to the child that it’s not yours?”

I had one for her, courtesy of my father, who had said with a mischievous gleam in his eye, “It’s like having an illegitimate child, isn’t it?”

I didn’t care about any of it, but there was still something niggling. I’d read interviews with grown-up test tube babies who felt upset or depressed by the thought of the clinical circumstances surrounding their conception. But could I really take such sensitivities into account? After all, I have never in my life dwelt on the circumstances of my own conception – and my parents started divorce proceedings within a couple of years of my birth, so who’s to say my conception wasn’t also a little sterile? Dismissed!

As it turned out, I enjoyed the painless minute-long procedure whereby two embryos were transferred by catheter into my womb. I started giggling the moment the smiling young doctor entered the treatment room, took one look at me with my legs in stirrups, rubbed his hands together and said something like, “Right, let’s get going!” It amused me that this jovial youth was going to try to make me pregnant; it was a wonderfully absurd situation.

On a monitor I watched two magnified embryos gently drift their way inside me. Two weeks later, Richard and I rejoiced cautiously at my positive pregnancy test. Four weeks after that, I had a scan in London and listened to the thump-thump-thump of two foetal heartbeats. We gulped – a lot – and laughed hysterically for a couple of days, but as the weeks passed leading up to the all-important 12-week scan, we began to take a more balanced view. It was intimidating, but thrilling, scary but brilliant; the upsides far outweighed the downsides.

Funnily enough, Richard is convinced he saw our donor when he went to provide his sperm, five days before I underwent the transfer. She would have been there to coincide providing her eggs on the same morning. Is it possible it was her? She was the only blond, blue-eyed, young-looking woman in the whole clinic, he said, which makes me think that perhaps it is. “She was really pretty,” he added, which was nice to hear, although I was much more interested in the only other detail of description he could give me when I grilled him: “She was reading a book.”

I am now five months pregnant with twins, and whether or not it really was our donor doesn’t matter in the end. Like any other expectant parents, we just can’t wait to meet our babies, whoever they are.

• All names have been changed.

• This article was amended on 27 March 2012. The original referred to a post-2005 collapse in sperm and egg donor levels. That has been changed to a shortage of sperm and egg donations.