The 38-year-old accountability coach is in her second trimester.
Teddi Mellencamp and husband Edwin Arroyave are expecting their third child together, but unlike their other two children -- daughter Slate, 6, and son Cruz, 5 -- baby No. 3 "was a complete surprise."
"I'm in my second trimester, 14 weeks," the 38-year-old accountability coach told Us Weekly. "Everything's good and I'm in the clear, so I'm just starting to get to that point where I'm sharing with everybody. Plus now I have a bump, so there's not much more hiding I'll be able to do!"
Teddi literally just walked in a New York Fashion Week runway show for co-star Kyle Richards' new resort collection with designer Shahida Clayton, where she successfully fooled everyone!
The Bravo star and her Skyline Security Management founder husband, 42, got married in 2011 and conceived Slate and Cruz through IVF.
"My husband said, 'I don't want to see you going through IVF again -- that was brutal,'" the daughter of musician John Mellencamp explained. "It was so many rounds, but this time we really weren't doing anything! I was on vacation! Just having fun with my family! It was a complete surprise. I didn't even know I was because I didn't have a regular cycle."
Even though the addition wasn't planned, Teddi said she and Edwin are "over the moon."
"I said to my husband, 'We don't even fit in our cars anymore!'" she joked. "Think about it, there's six of us! I'm like, 'We're going to start having to look at minivans! What's happening!?'"
"We have to really figure it out," she added. "We're like, 'Do we convert the playroom? What do we do?' We haven't even made those decisions yet, but we have to."
Edwin is also dad to 10-year-old daughter Isabella, who he has from a previous relationship.
"[The kids] are so excited," he gushed. "They've been talking about it for a long time and actually it's been my son who's been like, 'Mom, we need to have another baby,' and I never wanted to get his hopes up. So when we told him, he was through the roof. So excited."
"They're already calling it 'their baby,' and they have names picked for if it's a boy or a girl," Teddi added. "They're ready!"
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