The "GIRL" singer, 29, wore a blue two-piece gown for country music's biggest night.
Morris announced her pregnancy on Instagram, baring her bump alongside her husband Ryan Hurd.
"The irony is just too rich that after a year of living in the 'GIRL' headspace, the universe would give us a baby boy to even things out," Morris said in the announcement. "See you in 2020, little one."
Hurd, also a country singer, opted for a black and navy suit, which was left unbuttoned to show a little chest.
The two posed together on the red carpet.
Morris has six CMA nominations this year, more than any other artist.
Her nominations include Single, Album, Song, Female Vocalist, Musical Event and Music Video of the year.