Recently my children have started to ask various tricky questions about where babies come from. Until now I've managed to fob them off with pretty broad responses involving an egg and a seed and a baby growing in mummy's tummy. They seemed satisfied with my explanation and I was able to spend hours looking at websites that provided step-by-step instructions on how to divulge more information when the time was right, all the while thinking, rather smugly, that I had years to prepare.

How wrong can you be?

This summer my daughter Charlotte, aged five, asked me what 'sexy' was. I waffled something about girls getting dressed up and wiggling their bottoms which seemed to do the trick.

A few days later she accosted me again, this time in front of Tracy Beaker.

"How does the seed get to the egg?"

"What? Oh, errr, ummmm..." I faltered.

I do know I'm repressed; my sex education came at the age of 13 from a book that began: 'My cat has just had kittens.'

Panic started to rise, but I decided to be honest. I can do this: I'm a mature woman of the world, I said to myself. So here we go:

"Well, darling, when a grown up man and a grown up lady love each other..."

Cue a snorting noise from George - aged eight, and from Charlotte, a look of utter fascination. I was about to continue, but was well and truly stopped with:

"Does the man kiss the lady and the seed comes up into his mouth and goes into the lady's mouth and she swallows it and then it gets to the egg?"

Cue more snorting from George - who at the time was still pretending not to be listening but I could tell that I was beating Tracy Beaker in the ratings war. So where were we? Uh, yes: seeds and swallowing.

"No darling, that's not what happens. George, do you want to listen to this properly? I don't want to have to go through it all again later."

Click! Bye bye Tracy Beaker.

"Hold on a sec..."

I rushed upstairs to fetch the Children's Encyclopedia; there might be some useful phases and pictures in there that might save my credibility.