The couple announced they are expecting again in a video in which they talk about the book Everyday In His Presence by Charles Stanley.
At the end they say they were introducing a “special guest”, before Brittany stands up to reveal her “tiny little bump”.
Brittany said it was “a surprise” that she is expecting again, adding: “It was a surprise losing our daughter at the beginning of the year. That was tough, and still is.
“There are hard moments, but I went through a lot and I would still like to share my journey in some way that I can in the future.
“We don’t know what the future holds for my body physically going forward but here we are with another promise. We’re so excited.”
Lutz, whose other film roles include Immortals, The Legend Of Hercules and The Expendables 3, married TV host and model Brittany in 2017.