Well, I asked my father where babies come from at about the same age, and he sat me down and explained the whole works to me, beginning to end. It wasn't deadly clinical, but it wasn't so ephemeral so as to be meaningless, either. He just told me the facts, in simple, matter-of-fact terms.
And AFAIC, that's the best policy. Some time later, my friends at school got into a playground discussion about where babies come from. I listened to what they had to say, and I said, "That's baloney! Here's what my dad told
me!" One of the teachers overheard me and went into vapor lock (this was about 1968 or so); they ended up calling the Old Man at home and asking him if he had actually told me the Facts of Life, and he said yes, he had.
They wanted to know if he thought it was right to tell a 9-year old child the graphic details of the subject, and Dad (as he was wont to do when dealing with educators), rapidly exhausted his patience quota with them and replied, "Listen to me: if he is old enough to ask the question, then he is old enough to be told the truth, and not a a load of stupid b*llsh*t about 'the stork'. Now if you'll excuse me, I have work to do."

I'll have to say this: sex for me when I reached puberty was not that big a deal, and I think it's because the Old Man had removed the mystery and "forbidden fruit" aspect of it with that little chat we had when I was nine. I knew the facts of the subject, and I used to think, "Okay, so what's the big deal?" For all too many of my peers, however, that was something they lacked, and the more they didn't know about it, the more they cogitated on it.
Personally, I think it's better to be right up front with it and remove all the myths and misconceptions. Kids are not as squeamish about that stuff as parents are, I'm afraid. They're able to handle a lot more stuff than we give them credit for.
Anyway, that's my 2 cents worth.