How old is too old to be a mother?

So, a single woman of 66 is set to be Britain's oldest mother after having fertility treatment at a clinic in Ukraine - the kind of news that sets alarm bells ringing about unscrupulous IVF clinics, and allows for ethical debates about the rights and wrongs of helping women in their sixties to have babies.

It's true that we wouldn't raise our eyebrows very far at the prospect of a 66 year old man fathering a child, and it could be seen as sexist to be condemning a women of that age for wanting to have a child of her own. However, the very real risks for both mother and child of pregnancy at this age should not be underestimated.

What I can't understand is why it would take someone so long to realise that they wanted a baby? Surely, if you were so keen to get pregnant that you managed to arrange to go through donor treatment overseas in your late sixties, you could have done this at least ten years earlier...