Gillian anderson and Mark Griffiths attend the premiere of 'How to Lose Friends and Alienate People' at the Odeon cinema, Leicester Square on Sept. 24, 2008 in London, England.
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CelebNews@Usmagazine.com! - Gillian Anderson Gives Birth to a Boy

Gillian Anderson and her boyfriend Mark Griffiths welcomed a baby boy, her rep confirmed to Usmagazine.com on Monday.

Felix Griffiths, who weighed in at 6 lbs., 15 0z., was born October 15 in London.

Anderson and Griffiths are already parents to 1-year-old son Oscar.

She also has a daughter Piper, 13, from a prior marriage.

"The only thing I do when I'm pregnant is eat and sit on my butt!" the X-Files: I Want to Believe star, 40, told Us at the movie's Hollywood premiere in July.

See Us' bump hall of fame.

Her pregnancy cravings?

"I'm not really craving anything, but there's the lazy part of me that thinks, 'What's the point in working out until I have the baby?' Then we'll actually do something!" she said.

Check out photos of stars' post-baby bods.

Anderson told Us besides having "a couple of films coming out later in the year that I'll do some promotion for," she plans on focusing her life on mommyhood.

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