Thurman, who is best known for her roles in "Pulp Fiction" and "Kill Bill," has a son and a daughter with her ex-husband, actor Ethan Hawke. Busson has two sons with his ex-fiancee, supermodel Elle Macpherson.
Rumors have been swirling that Thurman is pregnant after it was reported she ordered designer duds in a larger size.
"She is absolutely not pregnant," Thurman's representative told Usmagazine.com. "She also did not order any clothes from Fred Segal. We are trying to find out if someone used her name to order clothes that were not meant for her."
Thurman and Busson have been dating for about a year and became engaged in June.
Puzzle-maker slips 'Murdoch Is Evil' into Rupert Murdoch's Sunday Telegraph
Exploding whale video goes viral on Internet