One of my coworkers is a university student who gets job experience working for us over the summers.
He and his fiancée are expecting their first child in the fall.
The pregnancy has not gone well for them. She is extremely high risk and has spent much of the time on bed rest.
She has problems with her
cervix and could go into labour at any time, without warning.
There are two doctor's visits a week and every week is a huge milestone.
The young dad-to-be is, naturally, very concerned and the pregnancy is a huge part of his attention right now.
However....
....when your fiancée gets permission from the doctor to attend the company barbeque, by all means, introduce her to your coworkers.
When they say they are happy for her that she is well enough to attend, you
could say something like:
"Thanks, we're happy things are going better and her doctor is pleased with her progress."
What you should
not say is:
"Yeah, her doctor says her
cervix is great and I'm all on top of that puppy!"

Surprisingly, she didn't scream at him.