Keep your leash on darling: Baby Brains by Simon James (New York: Walker Books, 2004.
I'm not sure it's the business of either children's books or science fiction to stomp on ambition and enthusiasm.
Baby brains is a very special baby who from the moment he gets home reads the newspaper. The next day he demands school and after sampling that he demands university and a week later is a surgeon in an operating theatre. Then space scientists ask him to go into space. He does, but realises he "Want my Mummy!"
"From that day on, Baby Brains spent most of his time at home doing the things that most babies do. Except, that is, at weekends when he still liked to help out at the local hospital."