The former Laguna Beach and The Hills star and her husband Jay Cutler welcomed a baby son called Jaxon Wyatt Cutler on Wednesday, 7 May. He weighed 7lbs 11oz.
Kristin announced the happy baby news via an Instagram post showing her hospital ID wristband, a baby's hat and a teeny pair of booties.
The star and her American footballer hubby are already parents to son Camden Jack, nearly two.
Kristin told Reveal last month that she and Jay already knew the name they'd give their second child, but were keeping it away from the public for now. "We actually had our name picked out before I got pregnant. It was left over from when we were deciding Camden's name. We're keeping it a secret though, so you'll just have to wait and see!"
She added of her pregnancy: "I've been feeling great, I'm lucky because I have relatively easy pregnancies, so I'm just enjoying the experience. It feels exactly the same as my last one and I've had absolutely no morning sickness, which is so lucky!"
Since her days on reality TV, the blonde star has started her own shoe line and currently hosts the E! trend show The Fabulist.
She married Chicago Bears player Jay in June 2013.
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Celebrities who welcomed babies in 2014 in pictures:
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