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