"The time has finally come to share our wonderful news that we are expecting our first child together," the singer said. "There are reports that I was in the hospital this weekend, and Kevin and I just want everyone to know that all is well. Thank you for your thoughts and prayers."
The couple were married in September. Magazines and tabloids have speculated for weeks that Spears, 23, was pregnant, documenting her expanding waistline and fuller figure, but she remained mum on the subject.
However, she has previously expressed a desire to start a family. In an interview with People magazine last fall, she said: "I want to be a young mom. I can see us as parents."
While this will be Spears' first foray into parenthood, Federline, 27, has two children with his ex-girlfriend, actress Shar Jackson. Spears and Federline met last year when he was a backup dancer on her tour — and Jackson was pregnant with their son.
Spears wed Federline just eight months after ending a 55-hour Las Vegas marriage to her childhood friend, Jason Alexander. Her second marriage has provided endless fodder for tabloids, which have speculated that the union is in trouble — prompting an angry outburst from Spears on her Web site last month.
Yet the couple have hardly hid from the limelight — last week, the pair announced they would document their courtship in a new reality series on UPN. The network promised "exclusive, never-before-seen private home videos" of their "personal love story."
Spears' impending motherhood may be the ultimate indicator that the former teen princess is all grown up. Spears was cast as an innocent with a bit of sex appeal when she made her debut at 16 with the multiplatinum " ... Baby, One More Time" and became a youth icon. As she grew older, her image got sexier, and more vampish.
Her last album was a greatest hits collection, which has sold nearly 1 million copies.
Last week, Spears and Federline said "I do" to star in a UPN reality series that documents their courtship, engagement and wedding.
Featuring what UPN bills as "exclusive, never-before-seen private home videos" of their "personal love story," the six-episode series is scheduled to premiere later this year. It picks up shortly after the pair met in Los Angeles and headed to Europe on tour, where Federline performed as a backup dancer for Spears.
UPN is also shooting new footage and commentary with the couple, who wed in September. It was the second marriage in nine months for Spears, who married childhood friend Jason Alexander in a surprise wedding in Las Vegas in January. That marriage was annulled 55 hours later.
Last week, the 23-year-old pop singer lashed out at tabloid magazines for reporting that she's pregnant and that the marriage is on the rocks.
"I feel that last year the tabloids ran my life," Spears said, in commenting on her new series, "and I am really excited about showing my fans what really happened rather than all the stories, which have been misconstrued by journalists in the past."
Said Dawn Ostroff, president of UPN: "Now, for the first time, their millions of fans will get to see and hear the couple's real story on UPN as told directly by them."
UPN and CBSNews.com are owned by Viacom, Inc.