Chrissy Teigen Showing Extreme Cleavage for Commercial Shoot

Chrissy Teigen is on a commercial shoot ... but from the looks of it, her dress is doing all the work.

Chrissy, John Legend and daughter Luna all showed up Monday for the shoot, which apparently requires Mom to show off some MAJOR cleavage.

She's about 5 months along with her second pregnancy, but she's clearly not slowing down a bit. In fact, she's still rocking some super-high heels.

While Chrissy's dress struggled to contain her ample assets -- John's super colorful tracksuit was fighting to get a little shine. Almost didn't see him there, right? It's okay, John ... hard to compete with the miracle of life.