The former Laguna Beach and Hills star confirmed the happy news was true on Wednesday afternoon (30 October), after several US publications reported a baby was on the way.
Kristin and husband Jay Cutler are already parents to adorable son Camden Jack, who was born in August 2012.
The couple married in a small ceremony in Nashville in June 2013 and later honeymooned in Italy.
Tweeting today, Kristin wrote: "Thank you for all the love!! We are so excited for Camden to be a big brother!"
American footballer Jay, who plays for the Chicago Cubs, was by Kristin's side during the birth, although she admitted afterwards that it hadn't all gone according to plan.
She told E!: "I was like, 'You're going to be behind me. You're not going to see anything.' "The nurse [said], 'Oh, no, no, he's going to hold your leg.' I was like, 'Oh, no he's not'. At that point I'm like, 'Whatever.' So he held my leg — he saw the whole thing."
The blonde star has made no secret of how much she loves being a mother, frequently sharing sweet snaps of her little man with fans.
Kristin told Chicago Now earlier this year she'd love four children – nearly halfway there now, Kristin!
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