Sienna Miller was ''delirious'' working during the early stages of her pregnancy.

The 30-year-old actress - who gave birth to Marlowe, her first child with fiance Tom Sturridge, in July - was exhausted in the weeks after she first discovered she was expecting a baby, but says it helped with her work on 'The Girl'.

She said: ''I was pretty delirious. I was filming during the first trimester. It was actually quite distracting. The tiredness was quite debilitating. And you can sometimes use some of that in your acting.''

Sienna planned to take a break after having her daughter, but changed her mind when she was offered a role in Bennett Miller's forthcoming film 'Foxcatcher', which was shot in Pittsburgh.

She told The Observer magazine: ''Though I know I had promised myself not to work so soon after the birth, it was too good an opportunity to turn down.

''Marlowe has been on about 15 planes already.''

The 'Factory Girl' star also spoke of a failed audition with an unnamed director while left her feeling ''violated'' when the filmmaker had an actor kiss her neck as she read a script.

She recalled: ''He had an actor in to read opposite me. We hadn't even been introduced. And the director told this guy to start seducing me and kissing my neck while we read. It was so weird.

''Eventually, I said, 'I can't do this.' And, of course, I was told I was difficult and all that.

''But I felt really violated for letting it go on for 10 minutes to try and get a job. And of course I didn't get the job But it felt so old-fashioned, so inappropriate.''