The former Hills star, 27, dressed her baby bump in workout gear and had a session yesterday (18 January) - despite her tummy getting rounder!
Posting a picture of herself in the slick-looking gym, Kristin wrote: "Gym selfie....baby bump getting big!"
In the snap, Kristin proves that pregnant women really do glow as she appears fresh-faced with no make-up and her hair tied back away from her face.
In black training leggings and a dark top, the only hint of colour is in Kristin's coral Nike trainers.
Kristin and her Chicago Bears quarterback husband Jay Cutler already have a son, one-year-old Camden Jack.
The couple announced they were expecting another child in October.
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Copyright: WENN Lexie Appleby/Future Image/Bridow/Instagram