The 37-year-old Maroon 5 frontman shared a photo of himself touching bellies with the 26-year-old model, joking, "Week 20 and I'm finally popping! #impregnanttoo."
Levine and Prinsloo have been together since 2012 and married in 2014. The couple announced they are expecting their first child in March. It's a girl.
"It's awesome. I mean, God, I'm going to be a dad," Levine told E! News last week. "I'm going to be a [expletive] dad. I'm going to spoil [Behati]. I'm not going to spoil the kid yet. Kid's not even out yet."
Levine confirmed he and Prinsloo are having a daughter on The Tonight Show starring Jimmy Fallon the same week. The singer revealed having children has "always" been a part of the plan, saying he's "super excited" to become a father.
"[Behati] is good," he added. "She's eating a lot of watermelon. Like, you know, because you get random cravings for stuff, and it's just like, so much watermelon. It's delicious. There's [ice cream], too. I eat a lot of stuff."
Levine last released V with Maroon 5 in 2014 and will resume his Maroon V tour May 28 in Lisbon, Portugal. The singer also serves as a coach on NBC reality competition The Voice, which airs Mondays and Tuesdays at 8 p.m. ET.