Beyonce upstaged every performer at the MTV Video Music Awards before the show even began, announcing she and husband Jay-Z are expecting a baby.

The soon-to-be-30 superstar arrived on the VMA black carpet holding her bulging belly while dressed in a loose-fitting, flowing red gown.

MTV tweeted the news, and photos confirming her motherly status soon circulated. Her publicist later confirmed the pregnancy.

In an instant, Beyonce and her unborn child managed to overshadow the night's events. Lady Gaga's much-hyped opening number, during which she performed as a greasy, leather-jacketed male alter-ego, became less important.

So did the evening's meticulously planned wild moments, from Nicki Minaj's origami-like outfit to a dance-off between the members of Odd Future and Jack Black, Will Ferrell and Seth Rogen.

Later, Beyonce performed Love On Top. Instead of her typical sexy outfits, she dressed in a conservative spangled tux - but still danced around in her signature stilettos.

Katy Perry, who had the most nominations coming into the show with 10, came away with three 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 honoured with an MTV Video Vanguard award for her visual legacy.

Adele had perhaps the highlight of the night as the seven-time nominee delivered a powerfully understated performance of Someone Like You, off her top-selling 21 album; she came away with three trophies on the night, tying with Perry.