Murgatroyd, 29, showed off her growing baby bump for the first time on Wednesday, sharing a pic of Chmerkovskiy kissing her bare belly on Instagram. The Dancing With the Stars champ gives a huge smile while rocking a sports bra and leggings, clearly enjoying the affection.
"We couldn't be happier. Baby Chmerkovskiy is coming," Murgatroyd captioned the adorable snap.
"They're so happy," a source told ET about the exciting baby news. "Funny thing is, they've been trying to get pregnant even before they were engaged."
Murgatroyd is now in her second trimester, and is expecting to give birth in January. She recently admitted to People that she was "so sick" during season 22 of DWTS due to her pregnancy, though you wouldn't know it -- she and partner Nyle DiMarco ended up winning the coveted mirror ball trophy.
"I'm looking forward to nurturing something and just having the baby be the center of our world," Murgatroyd told the magazine. "I'm looking forward to putting all our energy into this beautiful soul."
Meanwhile, Chmerkovsky just hopes the baby will take after his fiancee.
"We'll be in trouble with a little me running around," he joked. "So hopefully they'll be a lot like Peta."
Murgatroyd later revealed they're planning to tie the knot six months after welcoming their first child together.
"The baby will make a wonderful addition to the wedding party," Chmerkovskiy mused. "A wonderful, tiny addition."