14/05/2012 10:42 BST

Pregnant Sienna Miller Is Fit To Burst As She Celebrates Robert Pattinson's 26th Birthday

Sienna Miller's not got long until she's be knee deep in nappies, so she's got to make the most of late nights while she still can.

As she stepped out to celebrate Robert Pattinson's 26 birthday last night, the star was showing off her rapidly growing baby bump.

sienna miller

The actress headed to London's swanky Claridge's restaurant for a birthday meal in honour of the Twilight star, wearing a tight fitting grey dress with a belt underneath which accentuated her bump.

But her invite to the bash is a bit less random than we first thought, as it turns out Sienna's fiance Tom Sturridge is BFFs with R-Patz.

robert pattinson

The gang were also joined at the expensive London eatery by Hugh Jackman.

hugh jackman

Sienna spoke about her pregnancy for the first time back in March, but remained typically tight lipped about any further details.

She told Vogue: "It's all progressing nicely and it's very exciting.

"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."