It'll be interesting watching Kate gain a pound. If that...

Since we're guessing. I say Girl.

Name: Diana Elizabeth Camilla Sarah (they usually give 4 names, or so).

Or, if they're feeling "modern":

Apple Tuesday Mowgli Crimefighter

If I'm wrong, and it's a boy:

Charles Charles Philip Henry

Or, the modern version:

Chuckie Spencer Dweezil Fairychaser