The secret's been out for a while after her sister and stepmother confirmed the news.
And now Sienna Miller obviously feels ready to share her pregnancy joy with the world.
Glowing with mum-to-be happiness at a gala in New York, the star showed off her blossoming bump in a long dress, with revealing splits at the side.
Sienna, 30, and her boyfriend of one year, Tom Sturridge, 26, are believed to have told close friends and family around Christmas.
Romance blossomed when the blonde beauty was appearing in a play in London – Terence Rattigan's Flare Path – at the same time as the actor best known for The Boat that Rocked was in another theatrical production.
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