Sienna speaks!

Back in early January, Us Weekly broke news of Sienna Miller's pregnancy -- but the British actress, 30, has been absolutely mum about her first-time baby-to-be with fiance Tom Sturridge.

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Miller chose the April issue of British Vogue to break her silence. "I'm in my second trimester, so I'm I-can-talk-about-it pregnant," says the resolutely private star. "Even though I'm under strict instructions not to say anything as it would completely defeat the point of everything I've tried to achieve in the last eight years."

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(Miller was among the stars to take legal action against News of the World for violating her privacy via phone hacking and other tactics.)

Still, Miller offers that her first-time pregnancy is going well.

"I'm feeling fine...It's all progressing nicely and it's very exciting."

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Miller was similarly quiet about wedding plans with fellow Brit Sturridge, her beau of one year -- but she stepped out in London in mid-February with a dazzling engagement ring.

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