Beyonce, 29, announced her pregnancy on the red carpet by showing her baby bump. She later took the stage and performed "Love on Top."
At the end of the song, Beyonce took off her jacket and rubbed her belly. Cameras cut to her husband, Jay-z clapping and smiling as Kanye West jumped with joy behind him.
This is her first child with 41-year-old Jay-Z. The couple married in 2008.
Perry, who had the most nominations coming into the show with 10, came away with three moonman trophies, including video of the year for the inspirational clip "Firework."
"I feel like I'm doing something right when I sing that song," said Perry, conservatively dressed in a cotton-candy pink jacket, a skirt and something best described as a Green Bay Packer cheesehead decoration.
Britney Spears captured the night's first award, for best pop video, and later was honored with an MTV Video Vanguard award for her visual legacy.
The Associated Press contributed to this report.