The former The Hills star took to Instagram.com on Monday (23Nov15) to share the happy news, posting a photo of her new daughter's birth announcement and a pink onesie.

"Saylor James Cutler was born today at 132pm!!," she wrote.

Cavallari and Cutler, who wed in 2013, are already parents to sons Camden Jack, three, and Jaxon Wyatt, one.