Rebecca Frayn: I just wanted a baby. I didn't even care if it put my life in danger

Last week, further stories emerged about IVF mix-ups. Despite the risks, a mother confesses there was no stopping her quest for a third child

There must be many people like me, who having conceived children through IVF, shuddered inwardly when they heard an embryologist claim last week that basic safeguards were being routinely neglected in clinics across the country and that, as a result, mistakes are far more commonplace than people realise, including the alarming possibility of eggs and sperm from different couples being mixed up.

Sammy Lee, the embryologist who helped my husband and me in our quest for a child and a leading figure in the field, has been outspoken about the urgent need to tighten safeguards in the laboratory. Yet the ever-growing demand for IVF – in the UK alone 35,000 women are undergoing infertility treatment this year – can only make effective legislation ever harder to enforce. Meanwhile, rapid technological developments in what is possible make the ethical questions increasingly pressing and complex.

In the same week, concerns were expressed about women buying unregulated fertility drugs on the internet, while the pressure couples place on doctors to return more than one embryo despite increased risks has once again been in the spotlight.

The fact of the matter is, however, that many couples undergoing IVF are set on achieving a baby at any cost – often developing a kind of wilful moral myopia about the risks in order to avoid being deflected from their goal. I know, because it happened to me, too.

At first, perhaps because I was already the mother of twin boys when my husband and I embarked on infertility treatment and so could afford the luxury of ambivalence, I asked a lot of questions, humming and hawing about whether to proceed. During that period, it sometimes seemed as if I had thrown open a Pandora's box. Indeed, some years later the complex potency of the experience became the basis for my first novel, One Life, while my husband gave the storyline to Jimmy Nesbit and Helen Baxendale in Cold Feet, the hit series he was then executive producing for ITV.

So what were the issues that rose chattering and clattering out of that box when I peeked gingerly inside? There was, of course, the invasive nature of the whole business. Needles, internal examinations, dye sent through the fallopian tubes. The unpleasant realisation that suddenly the business of conception, which one had hoped to achieve privately and lovingly, now had a hefty price tag attached to it to pay for the team of virtual strangers to whom one must – in every sense – expose oneself. Somehow I brushed these uncomfortable details aside.

Hard on the heels of this unease came questions about the cancer scares associated with all the hormones I would be required to ingest. Liz Tilberis and Ruth Picardie, both journalists who died respectively of ovarian and breast cancer after many rounds of IVF, had often been cited as possible victims of science in this area. To attempt to achieve life at the potential expense of one's own is self-evidently sobering. Yet, even then, I somehow squared what I was contemplating doing with my conscience.

We live in times when science draws us on with the promise that we can be masters of our own destiny, so perhaps it was only to be expected that in attempting to play God in this way, I experienced one last attack of moral vertigo. For, in our case, there was another complicating factor to consider. If we proceeded, we would have to undergo ICSI – intracytoplasmic sperm injection, then still a relatively new development in IVF treatment. Used to treat men with a low sperm count, the eldest children conceived by this method were only seven years old at that point. When I Googled ICSI – as any self-respecting person wanting to inform themselves does now – the results were terrifying. Despite widespread use, not only had there been no clinical trials, but it appeared that a recent research project in the US had raised serious concerns over the development of children produced in this way.

I was astounded. A friend had recently conceived twins through ICSI and made no mention of these grave question marks. I could only presume she had averted her eyes. To seek to create life, knowing in advance that that life might be seriously impaired, was not something I could contemplate. So why did I not walk away? I suppose I was by then in the iron grip of procreation fever. I had come to embody Richard Dawkins's observation that "we are survival machines – robot vehicles blindly programmed to preserve the selfish molecules known as genes". Instead of moving on, I consulted the clinic's counsellor.

I told her I knew perfectly well I was extremely lucky already to be the mother of two beautiful boys; that I felt utterly ashamed to be possessed by a greedy longing for a third but, though it defied rationality, I couldn't shake the desire to conceive again. It was the counsellor who suggested I contact the senior embryologist at the clinic, Sammy Lee, who was also the pioneer of ICSI in the UK.

I rang Mr Lee and we spoke at some length. He was compassionate and understanding, confessing that he, too, had initially had doubts about the treatment. But he said he had encountered no health issues among the babies his clinic had produced, and he dismissed the research I had read as fundamentally flawed. It was a turning point.

So I set aside all uncertainties, we paid the substantial sum and embarked. I sniffed the hormones and then injected them. Twelve eggs were harvested and two fertilised embryos returned. I waited the usual fortnight, filled with despondency that it would never work. Yet miraculously, in the series of hurdles familiar to anyone who has undergone IVF, we had cleared the highest one of all. I was pregnant.

So did I hear the lid on Pandora's box finally snap shut now our goal was achieved? There was one last uncertainty still left rattling about in that box. Mix-ups in the lab. It's an issue no one dares raise with you directly if they know you are pregnant through IVF. For it is perhaps the haunting question mark of all. You may be carrying someone else's child.

It was so unsettling a prospect that, honestly, I never allowed my mind to dwell on it directly. By now I, too, had acquired the trick of wilful myopia. We were on our way, with a baby in sight. Mentally, I stopped my ears and hummed a little tune whenever the small voice of doubt threatened to make itself heard, and tried not to think about the black twins born to a white couple. Or about the clinic in the States where the chief medical practitioner turned out to have fathered a large number of the babies the clinic had produced.

Later, when I was writing my novel, Mr Lee was kind enough to show me around the laboratory he worked in. It was extremely odd to consider how human life could be conjured into being in this sterile setting. And it was easy to see how vulnerable to human error these precious elements of egg and sperm might be once they were cast adrift from their host bodies, stored like so many groceries in the humming incubator.

So when my daughter was born and people exclaimed that she was the spitting image of me, I can't deny the comment carried a particular resonance. Quite possibly, it was a resonance they – consciously or not – intended. After all, they'd read the same stories as me. In truth, the Pandora's box stays ajar for some while. Perhaps it wasn't even until some years later, as my daughter began to get to grips with school, that the lingering unease about potential developmental problems in ICSI babies at last evaporated. I finally heard that lid snap closed with a pleasingly audible click.

Rebecca Frayn's novel One Life is published by Simon & Schuster. Her next book, The Art of Self-Deception, will be published in spring 2010