"New release 2020! What a blessing!" Christina, 37, wrote while holding a photo of their baby's sonogram. "Let’s do this babe @mattpokora."
Matt, 33, shared a similar snap with the caption "La relève est en route! Legacy on the way!"
La La Anthony, Cassie, and many others wished them congratulations on their joyous news.
The two singers started dating in August 2017.
Christina caused speculation that they were engaged in June 2019, when she was spotted with a massive diamond ring on her ring finger while out in Los Angeles.
This will be Christina and Matt's first child.
She has a daughter named Violet with ex-husband The Dream.