The couple came out with the news Sunday during the broadcast -- and didn't have to say a thing about it either ... they let their actions speak for them. The Migos came out first for a medley songs, and were later joined by CB who was decked out in a revealing outfit.

And by that, we mean her massive baby bump was on display ... and, clearly, she's very pregnant. Looks like she's fairly far along too at this point ... at least 6 months, if not more.

BTW, Cardi didn't just come out to stand there and look pretty -- she was straight up performing on her own as well ... rapping to songs of hers like 'Type S***', and eventually getting shoulder-to-shoulder with her hubby as the audience went crazy with applause.

Up until now, this wasn't publicly known -- as CB has been laying fairly low of late. And now, it's obvious that was for good reason. Her team was on the ball too for this ... posting official pregnancy photos on her social media pages as soon as she took the stage.

This would be her and Offset's second child together -- of course, they also share Kulture ... who's all of 2 years old.