Joke about children

A three-year old walks over to a pregnant lady while waiting with his mother in a doctor's surgery.
"Why is your stomach so big?" - he asks.
"I´m having a baby." - she replies.
"Is the baby in your stomach?" - he asks, with his big eyes.
"Yes, it is." - she says.
"Is it a good baby?" - he asks, with a puzzled look.
"Oh, yes. A really good baby." - the lady replies.
Shocked and surprised, he asks: "Then why did you eat him?"