Christina Hides Her Surprise

Miss Aguilera hasn't yet confirmed her pregnancy, and she certainly wasn't showing it off at rehearsals yesterday with Tony Bennett.

I'm told the mama-to-be wore a top and a skirt that hid her baby bump. "It was yellow and white and really flowy," an onlooker reports. "It was sorta bohemian."

Hope she's extra careful onstage. I hear at one point during the performance she walks up some stairs to stand on top of a piano.

Also: Bennett's work won't end tonight with their duet. I just heard the legendary crooner is the surprise performer at the Governor's Ball!

—Filed by Marc Malkin