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.
Reportedly Matt spent over a year preparing his heart-warming proposal, putting a lot of thought into the design of the elaborate ring.
He had had it ready for months but was waiting for the right time to propose.
Ain't no other fans... Thank you Malaysia for all the love & support! XoXtina pic.twitter.com/oCVaYp1E8L
— Christina Aguilera (@xtina) March 28, 2014
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."