The Forgetting Sarah Marshall beauty and Parenthood hunk, 37, have been dating since 2007 and engaged since 2009.
The Hit and Run stars have been staunch in their stance to not tie the knot until same sex marriage is legalized in California, where they live.
Bell, 32, told the Advocate in February, "I don't feel appropriate taking advantage of a right that's denied to my LGBT friends.
"Dax and I have talked about it a lot, and this issue is very important to both of us. We’re just standing up for what we believe in. Period."
That same month, she told Vegas Magazine she and "consider ourselves already married…we already wear the rings. I don't want a wedding. It's too much stress."
Congrats to the expectant parents!