Pregnant actress Gillian Anderson showed off her expanding baby bump at the premiere of the new X-Files movie in Los Angeles last night.

The radiant star, who turns 40 in two weeks, stunned onlookers wearing a floor-length silk blue dress with a plunging neckline.

She is expecting her third child. Anderson and boyfriend Mark Griffiths already have a son, Oscar, who was born in November 2006.

Expecting: Gillian Anderson shows off her baby bump on the red carpet at last night's premiere of The X-Files: I Want To Believe

The actress already has a 13-year-old daughter, Piper, from a previous marriage.

Anderson recently admitted she found working on the action thriller a gruelling task, as she is not as fit as her co-star David Duchovny - so she left him to do the majority of the stunts.

She said: 'It was hard work. I'm too old for this. David's in the best shape of his life and did most of the work. He's climbing and jumping off cliffs. 

'I was more exhausted by the end of it than he was. I'm a wimp.'

The X-Files team: From left, Gillian Anderson, director Chris Carter, producer Frank Spotnitz and actor David Duchovny

The X-Files: I Want To Believe reunites actors David Duchovny and Gillian Anderson as FBI special agents Mulder and Scully.

The popular television show show officially ended in 2002 but the pair have teamed up again for the series' second full-length feature film.

And sneak previews of the new movie continue to tease viewers with Mulder and Scully's will-they-won't-they romance, hinting the couple may be getting close again.