The "Smile" singer, who is expecting her first child with boyfriend, Sam Cooper, was positively glowing when she hit the red carpet to support her mother, Alison Owen, who produced the film.
Although she looked fabulous in her vintage style dress, fringe bangs, and bold lips, Allen admits she's still self-conscious about all the weight she's gained.
"I'm aware of the fact that I've put on a considerable amount of weight," she tweeted in August after she announced her pregnancy.
Allen, 25, and Cooper, 32, have been dating for a year. She told Britain's Sun newspaper, "It goes without saying we are both absolutely delighted." The star suffered a miscarriage two years ago.
She recently told a British radio show that becoming a mom "is ultimately my main goal in life and more of a priority than flying around the world jumping up and down on stage singing songs."
What do you think of Allen's maternity style? Leave a comment below and click here to check out Alicia Keys' burgeoning baby bump in a white hot bikini.