No woman wants to hear "I can't believe how big you're getting!", even if she is pregnant.
Here are some welcome alternatives:
"You're looking so healthy!"
"Your hair looks great!"
"I've always said you had the best taste in literature of anyone in the company."
Truthfully, though, I'm in a good mood today. Will actually go see a movie (Harry Potter, natch) in the cinemas this weekend if all goes as planned. Hurrah! Enjoy, yo.