The actress rolled up to the event at the Hotel Bel-Air on Saturday afternoon along with Gwyneth Paltrow, Kate Beckinsale and Chelsea Handler with a massive cake and a whole host of other goodies for the mum-to-be.
According to an eyewitness, Gwen looked "radiant" as she arrived to greet her guests: "As she walked over the bridge and joined her friends she had a big smile on her face and was giving everyone hugs.
"There was a big welcome cheer for her and she seemed very grateful for all of the love."
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