Sienna Miller Gives Birth!

And baby makes three!

Sienna Miller and her fiancé Tom Sturridge welcomed their first child over the weekend in London, a source confirms exclusively to Us Weekly. Details on the baby's gender, name and weight were not available. The British duo have been dating for over a year and debuted signs of their engagement -- Miller's dazzling diamond engagement ring -- in mid-February.

PHOTOS: Sienna's chic bump style

After remaining mum about her pregnancy for several months, the actress, 30, finally opened up to British Vogue in April.

"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," the resolutely private actress expressed to the mag. "I'm feeling fine...It's all progressing nicely and it's very exciting."

PHOTOS: More pregnant celebrities

Despite the couple's silence about their new addition to their family, Miller and Sturridge, 26, made no hesitation in stepping out in public on several celebratory occasions.

PHOTOS: Incredible post-baby bods

In May, the couple stole some time away in Portofino, Italy for a babymoon. A week later, they got decked out to celebrate Sturridge's BFF Robert Pattinson's 26th birthday at Gordon Ramsey's restaurant in London, England.

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