When answering awkward questions for our youngsters, it has proven useful, being keepers of pigs.
He asked again at bedtime when Mummy, a reliable source of accurate and well-explained information on many topics, was available.
Offsetting the answer into the world of pigs is a really useful mechanism, in that it softens the nature of what you're about to say, which can be alarming to an 8 year old. After all, nothing like his stuff happens in the Lego movie.
So I explained what Kevin the Berkshire boar puts where, and how some seed shoots out at high velocity and finds an egg inside Rosie the Saddleback sow, and then together the seed and the egg grow into piglets. Or a baby. Smudge was smiling shyly and evidently following, but clearly still needed clarification.
'So is it the same in humans?' he asked.
'Yes,' I replied in my best pragmatic manner, whereupon I could see him making some quick calculations in his head.
'So you've had to do that twice?' he said.
I know that you're not supposed to laugh when having a discussion of a sensitive nature with your child, but I'm afraid that's the point at which I lost it.