The couple tied the knot in 2019.
"I felt like a dad today for the first time," Haibon raved. "I'm learning so much!"
"We have an appointment next week where we’re going to find out the sex of the baby," he added. "It will be cool when we go. We can see, like, a foot."
Iaconetti, 33, and Haibon, 32, also revealed that later on Thursday they'll be posting a video to their Instagram pages, of the moment they found out they were expecting.
The couple's newest addition did come later than fans expected, as they told ET in 2019 that they hoped to have a baby the following year.
"We talk about it a lot," Haibon told ET at the time. "We both want kids."
Iaconetti and Haibon appeared on seasons 2 and 3 of Bachelor in Paradise in 2015 and 2016, though both instances ended with a friendship, not a relationship, for them.
Iaconetti went on to win Bachelor Winter Games with Kevin Wendt, who she dated after the show. Months after Iaconetti and Wendt's split, Iaconetti shocked fans by revealing that she was dating Haibon. The couple got engaged just months later, and tied the knot in 2019. They will celebrate their second anniversary in August.
As the couple prepares for their new arrival, take a look back at their wedding day in the video below.