Bump's out, and Kristin Cavallari's proud! The former Hills star took to Instagram on Saturday, Jan. 18 to show her second pregnancy's progress in an all-black workout ensemble. 

PHOTOS: Kristin's chic pregnancy style

"Gym selfie….baby bump getting big!" she captioned the picture. 

The shoe and accessories designer recently celebrated her 27th birthday with hubby Jay Cutler and a "mocktail." The couple, who wed in June 2013, shares son Camden, 17 months.

PHOTOS: Kristin Cavallari's life as a mother 

Cavallari told Us Weekly that for Christmas, their doctor put a note with their second child's gender in it, and they opened it on the holiday. But they have since remained silent about the child's gender on social media. 

PHOTOS: The Hills stars, then and now

In September 2013, Cavallari told Us Weekly, "I would love to have a little girl, but if i had another boy, that would be great too." 

This article originally appeared on Usmagazine.com: Kristin Cavallari Shows Off Her Baby Bump in Gym Selfie: Picture