After dominating the box office with pooch flick "Marley & Me", Jennifer Aniston escaped to Cabo San Lucas with beau John Mayer to celebrate New Year's -- but is the couple also celebrating an addition to their twosome?

That's false. The New York Daily News floated a rumor that Jen is expecting, after sources say someone shopping for Mayer placed an order for baby clothes -- but "Extra" talked to reps for the "Body is a Wonderland" singer -- who nixed the report.

Aniston and Mayer have been dating on and off since April.