The day I was born, my mother was about to turn 24 and my grandmother was 46. When my daughter was born in 1996, I was 35 and my mother was 58, still full of vim and ready to lend much-needed practical help to her career-minded daughter, who had been working so hard since she left university that she had seldom seen her own house in daylight.
Reader, I confess it, I was a stranger to my own Kenwood mixer.
If my daughter follows my timeline, I will be at least 70 when my first grandchild is born – if she finds time to fit in babies at all, that is. Hardly a given in an era when one in four female graduates on this side of the Atlantic will never have children.
I really, really want to be a wonderful, active grandmother, not least because I feel that I missed out on too much of my own children's precious, talc-scented babyhood, being back in the harness faster than you can say: "File by five o'clock."
So, recently, I have taken to saying the unsayable to my girl. "If you find a lovely man in your early twenties, you can have your babies then, darling. The rest can wait."
This is heresy for a feminist raised in the Seventies on the gospel of Having It All. It pains me to know I am a traitor to the cause in which I believed so passionately.
My generation of female graduates just knew that we would have a career first, get ourselves established, then marriage and children would show up at some indeterminate point – quite possibly delivered by a stork in a premium time slot booked at our convenience.
Certainly that time would not be before our mid-thirties. So quickly and firmly embedded did this new template for reproduction become that women who had their babies before they were 30 began to be regarded as mentally deficient child brides.
Sophie, who works in PR and got pregnant at 26, told me recently that she was treated as an object of curiosity and sympathy.
A couple of Sophie's friends actually asked her if she was going to have an abortion, assuming that the baby was a mistake.
When Sophie said that the pregnancy was planned, her professional women friends shook their heads in amused astonishment and told her she must be mad.
Yet, according to human biology, it is Sophie who was sensible and her friends who are the crazy ones.
Most hit puberty in their early teens, which meant the eggs they were born with had been ready for action for around 13 years.
That's a long time to leave eggs on a shelf. By the time those women planned on starting a family, say at 35, the eggs would have been waiting to be fertilised for at least 20 years, and getting pregnant would be twice as hard.
It's an extraordinary idea. Millennia of evolution have been overturned in a few short decades in order that women can succeed in a man-made hierarchy.
So three cheers for Kirstie Allsopp. The robust, plain-speaking presenter of Channel 4's Location, Location, Location said this week that she believes women are being let down by the system. "We should speak honestly and frankly about fertility and the fact that it falls off a cliff when you're 35," says Allsopp.
"At the moment, woman have 15 years to go to university, get their career on track, try to buy a home and have a baby. That is a hell of a lot to ask someone."
She's right, isn't she? I'd never thought of it quite like that before – though, on any occasion when I find myself addressing a group of women in their late twenties, I tell them that, if they have a presentable male on the premises, they should go home that same night and have unprotected sex. This instruction is usually greeted with embarrassed giggles and protestations that: "I can't get pregnant now because (delete as appropriate) it's not the right time; we haven't got enough room in our flat; I'll lose my bonus; if I just wait another few years, I'll be more established in my job and it will be easier to take a break (it won't be)."
My crusade came from the sense that, like Kirstie Allsopp, I was extremely fortunate to be a mother at all, having left it late in the day.
Close friends were not so lucky. "I only whistled in there by a miracle," says 42-year-old Allsopp, whose sons are aged seven and five. Her honesty is as refreshing as it is rare. Most celebrities airbrush the trauma and difficulty of having babies in your late thirties and forties; it's easy to make it look easy when you have outsourced the conception and the carrying.
The 41-year-old model Caprice Bourret recently took the hotly-contested prize for Most Absurd Celebrity Mum when she had her sons, Jett and Jax, one by a "gestational carrier" and the other as nature intended. Obviously, the latter was a mistake because having babies oneself is rather vulgar, frankly. So Jett – or was it Jax? – was born a month earlier than his brother in a different country to a woman other than his mother. Caprice says she has no regrets about going down the surrogate path because: "I don't think I would have gotten pregnant otherwise." It doesn't seem to have occurred to her that Kane and Abel – or Jett and Jax – might take a less sanguine view of this fraught fraternal fandango. Far better if she had admitted: "I was a fool to leave it so late."
Kirstie Allsopp is not preaching from a privileged pulpit, as critics have charged. Yes, she can be irritating, with her homespun, crochet-your-own-cervix shtick but, through her willingness to share her mistakes, she is at least trying to spare the next generation of women the heartache she has seen among friends who have struggled to have a child.
I like her observation that it's hard to make equality work in practice when "women have this time pressure which men don't have...If everyone started having children when they were 20, they would be free as a bird by the time they were 45."
Another factor, rarely reported, is how pulverisingly knackering motherhood is the older you get. A 24-year-old can party till 4am, then get up the next day for work. At that age, a jagged run of broken nights with a teething baby is just clubbing without the Bacardi Breezers. "At 36, with my third baby, I felt that physically I couldn't cope nearly as well as I did when I was younger," reports Emma, a mother of sons. "It was shattering." That seems to be a common experience, yet postponing motherhood grows more popular, not less, with the number of mothers over 50 doubling in the past five years. Facebook chief operating officer Sheryl Sandberg hasn't helped, with her ludicrous suggestion that ambitious young women should "lean in" to their work at exactly the time they should be leaning back and getting pregnant.
Where I disagree with Allsopp is when she says she would tell a daughter of hers not to go to university. "Start work straight after school, stay at home, save up your deposit – I'll help you, let's get you into a flat. And then we can find you a nice boyfriend and you can have a baby by the time you're 27."
Now that really is the voice of hereditary privilege talking through its trust fund. Even if we could, I don't think many mothers would go back to the bad old days of Mrs Bennet in Pride and Prejudice, desperately seeking sons-in-law for our uneducated girls, who were nothing without a man. Besides, university is a top place to meet a suitable mate.
Education remains the best springboard to equality that we have. The conundrum is that the higher the education and the steeper the career path we put our girls on, the farther they get away from what Mother Nature intended, with often devastating results. We need companies to come up with creative solutions to help women combine work and motherhood more effectively throughout their lives. If you can be a clueless trainee at 18, why can't you be a trainee at 45, when you are rich in the life experience of raising a family?
I'm not the only woman who feels she'd like to become a grandmother while she's young enough to be of use, or even alive. Am I? We need a revolution in our thinking about the right time to start a family. If Kirstie Allsopp can track down a property to suit any budget or taste, then she is just the woman to lead the campaign. Now, Kirstie, if you could just find a well-appointed young man with great potential and outstanding views for a certain daughter of mine ...