Pregnant Keira Knightley is frustrated she will not be able to enjoy a boozy celebration at Sunday's (22Feb15) Academy Awards ceremony.

The British star is nominated for the best supporting actress prize for her part in World War II drama The Imitation Game, but her mother-to-be status means she will be teetotal at the glamorous event.

Knightley reveals her husband, Klaxons rocker James Righton, will be making up for her sobriety by drinking for two.

During an appearance on The Ellen DeGeneres show, she says, "I can't drink! I'm up for an Oscar and I can't drink at the Oscars! I went to the doctor, you have lots of doctors check-ups when you're pregnant, and she was like 'Any questions?' and I was like, 'Yes, when can I drink? Please! I just want a margarita!' My husband's having a great time, I'm eating for two and he's drinking for two. It's brilliant. There's a lot of free Champagne, so he thinks that because I'm not drinking the Champagne he has to (drink) all of it."