Pop star Britney Spears [ tickets ], during a Tuesday (5/9) appearance on CBS-TV's "The Late Show with David Letterman," said she's pregnant with her second child.

"Don't worry Dave, it's not yours," Spears told Letterman.

Prior to her Letterman appearance, it had been widely speculated that Spears--who gave birth to a son, Sean Preston, eight months ago--was pregnant again, with tabloids and entertainment magazines publishing pictures of an apparently pregnant Spears in recent weeks.

Spears, 24, and her husband, Kevin Federline, 28--a former backup dancer who is trying to launch a career as a rapper--were married in 2004.

The couple's experience with their first baby has been less than smooth. In a well-publicized incident, Spears got a visit from authorities after she was photographed driving in a car with her son--required by law to be in a car seat--in her lap. She got another visit in April after her son reportedly fell from a high chair.