Rachel Zoe stepped out on Dec. 29 for the first time since giving birth to son Kaius one week earlier Credit: AKM-GSI

It's hard to believe she just gave birth! Rachel Zoe looked as slim and as chic as ever while brunching at L.A.'s Bel Air Hotel on Sunday, Dec. 29 -- just one week after she and husband Rodger Berman welcomed their second son, baby boy Kaius.

The 42-year-old fashion designer was stunning in a flowy black dress under a black blazer, with lots of chunky necklaces and a pair of oversized sunglasses. She was accompanied by son Skyler, 2, as well as newborn Kai, who was wrapped cozily in a blue blanket.

Zoe and hubby Berman, who married in 1996, announced baby Kaius' birth on Dec. 22. "So excited to welcome our baby boy into the world...he's 7 lbs, 12 oz, beautiful, healthy, and we couldn't be happier," the celebrity stylist tweeted.

The next day, she shared a photo of the little bundle of joy swaddled in a blanket. "I wanted you to be the first to see a picture of the beautiful new addition to our family, Kaius Jagger Berman, a.k.a. 'Kai,'" the second-time mom wrote on her website, The Zoe Report. "Rodger, Skyler and I are madly in love and will be happily hibernating for the next couple of weeks. Thank you for all of your kind words, as they mean so much to us."