ET's Nancy O'Dell caught up with the 36-year-old country singer at the 2019 ACM Awards in Las Vegas, Nevada, on Sunday, and she opened up about fitting into her stunning, sparkly, black-and-silver, one-shoulder Nicolas Jebran gown for the annual ceremony just months after welcoming her second son, Jacob.
"I am zipped so tight in this dress ... it's pushing things up to places where it doesn’t normally go," she quipped.
Underwood also addressed her nerves about both her body and her singing voice after welcoming Jacob with husband Mike Fisher, with whom she also shares 4-year-old Isaiah.
"My body is completely different than when it was a few months ago, and it’s always weird, kind of, to come back and [ask] ... do I still have it? Can I still sing?" Underwood said. "Because I had an obstruction in this area for nine months, and now it’s gone. And it’s an adjustment period and it’s on the early side of me."
"It’s the ACMs, I had to come. I wanted to perform," she added.
As for baby boy Jacob, Underwood revealed that the little guy has "just started laughing, which is the sweetest sound in the whole world."
"It’s getting bigger and bigger and he’s just making laughing noises and it’s like, ‘Was that a laugh?'" she said. "And now it’s getting more and more. And he’s such a smiley baby, and so was my other son. They’re special when they’re smiley."
Before hitting the stage to perform Sunday night, Underwood gave fans a peek at how she was preparing. The multi-tasking mama revealed she was warming up, while also "pumping."