I never wanted children, so I went to the doctor at 21 and asked to be sterilised. She briskly sent me away to “think about it”, and life took over. Thank goodness I never went back, because, at the age of 43, I had my one and only, wonderful child. Something I thank not only my lucky stars for, but every single sparkling dot in the firmament. As a consequence I’ve learnt never to say never.

Why did I leave it so late? Like many women who were feminists in the 1970s, I put my career first. I was ambivalent about children – there would be time “later” if I changed my mind. And when 40 loomed, later was suddenly upon me with a vengeance. Also, I never met the right man – until almost too late. Plus, there were psychological reasons – I never really felt grown up enough until I had enough therapy under my belt to contemplate parenting a child. There were overwhelming physical reasons: I had suffered crash injuries in a nasty road accident at 17 and been told by a grim gynaecologist that I should forget about children. This was coupled with having a rare rhesus negative blood group. All in all, it seemed pretty risky business.

At 40 I was single (having ended a 10-year marriage to a man who didn’t want children – at least with me) and writing my first book. I thought, “Well, if this is as good as it gets, then it’s OK.” Then a cat moved into my house. I’m allergic to cats and spent days booting it out, only for it to scootch back in again. I cracked and bought cat food. Then the man followed in the cat’s wake. He turned up unexpectedly and seemed a very unlikely candidate, but I knew, almost instantly, that this would be “it”. A year later we were living together and trying for a baby – for the first time in my life.

I got pregnant amazingly quickly – in seven months at 42 – and the pregnancy was extraordinarily uneventful. I had been told so many times it would kill me, I would be unfit, I couldn’t cope – and yet I loved every minute of it. I rushed to bookstores to look for inspiring reads and kept reading that I was definitely over the hill at 35. Pregnant women over 40 hardly got a mention – we were either a forgotten breed or a sheer embarrassment. So I drafted my book outline, and only when Cherie Blair’s pregnancy at 45 rocked the nation did I zap it to my agent, who sold it instantly.

And the time for women to have babies over 40 has definitely come. Although only 2 per cent of women give birth over 40, the figures are set to rise as the century progresses. With technological leaps and medical breakthroughs, it is increasingly possible to urge women into fertility, as in the recent case of Lynne Bezant who gave birth to twins at 56 post-menopause (her husband had had a vasectomy, too). It may well become a trend for women in their twenties and thirties to freeze their embryos as a matter of course, and defrost and fertilise when ready with the right person (or even alone).

Of course, health risks are greater over 40 and it would be naive to gloss over them. The risk of Downs and other abnormalities increases from one in 1,500 for a woman in her twenties, to one in 750 in her thirties, to a staggering one in 100 after 40 and one in 40 after 45. However, this increased risk is counterbalanced by increasingly sophisticated tests and scans. Within a couple of years it should be possible to detect birth defects in the early weeks through a simple blood tests which should replace the riskier amniocentesis and CVS (chorionic villi sampling) techniques. Even now, a nuchal fold scan is available at around 11 weeks to measure the baby’s neck, a test that is now offered routinely in many areas to screen for Downs.

Another risk is the increase in miscarriage. “For a woman over 40, the figure is about 25 per cent – one in four,” explains Professor Lesley Regan of the Recurrent Miscarriage Unit at St Mary’s Hospital in Paddington. “Whereas for a younger woman with no previous history of miscarriage, and no medical problems, the risk of miscarriage may be as low as five per cent.” Indeed, I went on to have four miscarriages myself after successfully having my daughter at 43.

I was referred to Professor Regan who put me through a battery of tests and who could find no obvious cause. It was probable that my remaining eggs were past their sell-by date. However, Professor Regan was positive and hopeful and sent me away to keep trying. At 45, I decided with my husband that having had five pregnancies in three years was enough physical and emotional wear and tear. After all, I had a wonderful two-year old and I might miss her childhood trying for other children.

Indeed, this is a common issue for older mothers who, having tasted the fruits of their own labour late in life, suddenly want more children. Some go on to have more children. Indeed, one woman I have interviewed had three boys after 41. Others are unable to, like me, and some decide to adopt or foster deprived children as a consequence. Again, to counterbalance the negative effects of being an only child (lack of social skills, sharing, etc) I found most of the mothers worked extremely hard to make sure that their offspring attended playgroups, had friends round, and were part of a wider family group.

Another risky issue is multiple birth. There is an increased risk of having twins or triplets over 40 as the ovaries can eject more than one egg a month and the menopause draws near. I have to say I could feel the urgency within my body to procreate. The ovarian drum was beating, along with the biological clock. This was confounded because, as a diehard feminist, I would always have come down on the nurture side of the argument over nature. But the urge to have a baby was a definite pull – which I call the desire to “get on in before closing time”.

I found many women, who had not only finally found a Mr Right late in life (after being single for years or married to the wrong man), and who simply could not let the issue of having a baby go. Many of them had been written off 20 years ago by the medical profession, or had been so badly butchered though miscarriage or medical bungling, and had resigned themselves to not having children. Some had had cancer, abortions, failed IVF, ME (Myalgicencephalomyelitis) and had felt that having children was impossible. And some had “accidental” pregnancies, something which is not uncommon over 40, or even 50 (I discovered that there are as many abortions for 50-year-old women as the under 16s). Older women simply don’t think of themselves as fertile as the menopause approaches or even starts, yet the risk of getting pregnant is still there and some women find themselves in a serious dilemma – to go ahead or abort at 40 plus.

There is a “forest of myths” surrounding women over 40 having babies which I want my book to scotch. Women are still disparaged more than men for procreating late in a way that is, dare I say, sexist. Lynne Bezant was largely slated by the press as being “selfish” and “thoughtless” about having children at 56; whereas Eric Clapton is applauded for taking a risk at the same age. We worry about being an embarrassing granny at the school gate. But older children always think that their parents are cringe-worthy and an older mum will have more panache and confidence in dealing with any jibes.

The research undertaken by Julia Berryman, senior researcher at the University of Leicester’s Parenthood Research Group, has underlined the value of older mums in particular. Her findings show that children of older mums do better at reading and comprehension tests and have well-developed social skills. Equally, her findings show late mothers to be more patient, calm and steady than their younger counterparts. Indeed, many of the women I interviewed were happy to stay in, even give up high-powered jobs, to enjoy their progeny. Plus, the issue of having enough energy as a parent is a universal one and in the end it is very much an individual thing how energetic you are. I certainly have as much energy as a thirty-something woman, if not more, and I also know some 30-year-olds who are positively ancient in terms of their energy and outlook.

As for the future, there is no denying that I will be 63 when my daughter is 20. She may loathe the fact that I’m “so old”, or she may be extremely happy that she had a mother that really wanted her and loved her to pieces (without smothering her or living through her vicariously). I certainly do my best, as most late mothers do, to keep fit and healthy. I watch my weight, alcohol intake and take regular exercise.

It’s a cliché, but 40 is not only the new 30, but 50 is the new 40. Gone are grey cardis, hairnets and slippers – women are sassier and sexier than ever before, regardless of years. Anyway, my daughter’s lifespan could be 130, and I’m planning mine to be at least 90.

And if I pop my clogs early, I just hope she enjoys the fact that she won’t have to look after an aged mum and may well have a bob or two to enjoy doing what she wants to do with her own life, before it’s too late.