Speculation mounted after the 29-year-old singer appeared on the American Music Awards to perform an extract from her latest film Burlesque, wearing a tight bodysuit.
OK magazine commented, 'Her wardrobe last night has also been fuelling pregnancy buzz as the crooner appeared to have gained some weight since her title role in Burlesque.'
But a friend of the star insisted that Aguilera - who announced her divorce from husband Jordan Bratman earlier this year - is not pregnant.
'She is going through a hard time, getting divorced, opening a film (Burlesque) and caring for her son and hasn't had time to work out,' the source said.