The season 25 mirrorball champion also posted a full video from her at-home gender reveal celebration via YouTube. The video shows Arnold and Cusick's family members all taking bets on whether it's a girl or boy, and the two jumping into each other's arms after a can exploded with pink confetti.
"I'm literally shaking," Arnold said. "What is happening!"
"Oh my god, I gotta process this," Cusick added. "You got your wish."
Earlier this week, ET spoke with the parents-to-be via Zoom, before they knew their baby's gender. Arnold revealed that she and Cusick had been trying for a baby for a while. She said she actually learned that she was pregnant while on tour with her fellow DWTS pros. Cusick, meanwhile, was on a trip and did not have cell reception.
"I found out I was pregnant on tour in a hotel room by myself. I had a day off, and I think I was in Kansas City. I just remember waking up that morning and being like, 'I think I am pregnant, I think I am.' So I went to CVS by myself, I got a test and took it," said Arnold, who's due in mid-November. "Sam and I saw each other about a week after. I kind of debated if I would tell him over the phone, and I was like, 'No, I absolutely have to tell him in person.' So I kept the secret to myself for about a week and it was very hard, if you know me."
Despite having to keep it a secret for so long, Cusick was, indeed, the very first person Arnold broke the news to. He told ET that he definitely got a little emotional after learning he was going to be a dad.
"I am not a crier, but I cried," he admitted. "I was crying, I was so happy. That does not happen very often with me! I can't remember much besides crying and just being happy."