"Because, you know, they get random cravings for stuff and it's just like, so much watermelon!" Levine added. As far as cravings go, you can't do much better than watermelon, although he admitted that she also has the occasional craving for ice cream as well.
The Maroon 5 frontman, who confirmed he's "super excited" that the couple is having a baby girl, also told Fallon that he and Prinsloo have wanted children from the start.
"It's always been part of the plan," Levine, 37, explained.
The singer recently shared similar sentiments with ET at The Voice's Karaoke for Charity event last week, where he said, "I'm ready to be a dad. You're born to be a parent, that's what we're here for, really. All the other s*** is great, but it's not what we're here for."