The fashionista announced the arrival of her second child via Twitter on Sunday night (22 December), writing: "So excited to welcome our baby boy into the world...he's 7 lbs 12 oz, beautiful, healthy and we couldn't be happier."
Rachel and husband Rodger Berman are already parents to son Skyler, two.
They haven't confirmed their new arrival's name.
Rachel, 42, kept mum about her pregnancy for a long time before confirming a baby was on the way in September via a post on her official website.
"Rodger, Skyler and I hope that everyone had an amazing summer!" she wrote. "Before we head into the chaos of fashion season, we wanted to take a moment to OFFICIALLY confirm that we are expecting another child.
"We are beyond excited for Skyler to have a sibling and for us to fall in love all over again. We feel incredibly blessed. Thank you all for your constant love and support of our family."
Congrats to Rachel and Rodger!
Check out more celebrities who welcomed a baby in 2013 in Reveal's gallery below!
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