Fergie will tonight host the glam Life Ball in Vienna. The pregnant singer is headlining the costume gala, at the sumptuous City Hall, to fight AIDS. Fergie has added her own twist, making the event a ball celebrating the dance form of voguing. We’re told that a Life Ball plane left JFK yesterday packed with professional voguers, who “danced during the entire flight. They were having dance-offs; it was wild.” Fergie herself, expected to give birth this summer, took a different, quieter flight. A source tells us, “This will be her last trip before she gives birth. She wanted to get some rest before the ball.” Guests expected include Bill Clinton (who perhaps won’t be voguing) and Kelly Osbourne.