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.
"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.