The pop singer and mother to son Max, aged 6, revealed the news onstage at a fan event in Malaysia today.
Afterwards she tweeted: "Ain’t no other fans… Thank you Malaysia for all the love & support! XoXtina"
CLICK THROUGH FOR A GALLERY OF CELEBRITY MUMS-TO-BE IN 2014
The 33-year-old is engaged to Matthew Rutler who proposed back in February,
On Valentine's Day, Christina announced their engagement via Twitter. "He asked and I said….," she wrote alongside a sweet photo of her diamond-adorned hand holding film producer Matt's in front of a romantic beach setting.
The pair have been together almost three years. They first met on the set of her 2010 film Burlesque.
Christina's musical legacy earned her a spot in Time magazine's 100 most influential people list in 2013, and the bumper issue featured a glowing review of each entrant written by another high-profile figure.
Fellow singer Celine Dion was full of praise for Christina, describing her as "beautiful" and saying her vocals were "flawless".
Christina on stage in Malaysia
"Without a doubt, she's one of the most talented artists the world has ever seen and heard, and I think she's going to continue to amaze us for many, many years to come," Celine added.
For several years Christina was a coach on the US version of The Voice but left her seat last year.
In recent years, she has been a passionate defender of full, healthy figures in Hollywood. Discussing her weight recently she said, "Actually, the challenge I've always had is being too thin.
"So I love that now I have a booty, and obviously I love showing my cleavage."