"Our team is expanding and we couldn’t be more excited!! Baby Lambton will be here in December and Lyla James is ready for her promotion to big sister!" Peyton captioned a sweet family shot, as Chris reposted the image, adding "Woooohooooooo."
In a post on her blog on Tuesday, Peyton called her pregnancy a "complete surprise" after she and Chris conceived Lyla through IVF. "We went through so much to bring her into this world," she explained. "I just assumed that was how we would create all of our babies... boy was I wrong!"
Peyton, who competed on Andy Baldwin's season of The Bachelor in 2007, married Chris in 2012, two years after he competed on Ali Fedotowsky's season of The Bachelorette. Lyla was born four years later.
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"How in the world is it happening now?" the former reality star wrote on her blog. "I had a plan. I was going to enjoy the summer with Lyla James and then start the madness in the fall. God and the universe had other plans for us and we couldn't be more excited!! I feel a bit of empowerment that my body was able to do its job. I'm happy that IVF exists and I am also happy to have a different experience this time around."
"I have been sick as a dog, but I am finally coming around as we just passed the first trimester," she revealed. "The exhaustion is no joke, especially with a very active toddler running around."
But Peyton, who is waiting to find out the sex of baby No. 2 until he or she is born, said she's sure Lyla will be a great big sister.
"She is so nurturing and loves taking care of her baby dolls so I think and hope that will transfer into a real baby," she wrote. "Fingers crossed!"
Chris and Peyton aren't the only success story to come out of Bachelor Nation. Watch below.