The video shows what appears to be an ultrasound of a fetus with the words "Mini Buble !!!" attached to the image.
A written statement that also is part of the 21-second video says, "We're having a baby Bublé!!!"
Bublé, 37, is a three-time Grammy Award winner known for such songs as "Haven't Met You Yet," "Home" and "Save the Last Dance for Me." He is playing five nights at the 02 in July.
He and Lopilato, 25, were married in 2011. She has starred in such Spanish-language television series as "Chiquititas, la historia" and "Rebelde Way" and has also worked as a model.