Johnson, 27, shared a photo of herself on Instagram rocking the red, white and blue leotard while 40 weeks pregnant. The gold medalist said it "fits a little different these days."
"But no joke... this babes is already more rewarding than any medal was," she added.
The baby will be the first for Johnson and her husband, Andrew East, but the journey to becoming parents hasn't been easy for them.
The couple spoke candidly about the emotional toll of having a miscarriage in a heartbreaking video posted on YouTube in October 2017.
"The day that I was told we were miscarrying, I felt guilty," Johnson said. "I felt sad. And I remember telling Andrew, 'I'm sorry I lost your baby.' I felt like it was something that I did."
Two years later, the couple couldn't be more excited to be first-time parents.
"BABY! GET HERE ALREADY!" Johnson wrote next to her Instagram photo.
We're wishing Johnson and East all the best as they prepare to welcome their new baby into the world!