It means they’re having bareback sex and the man orgasms while inside her.
It should not be tolerated at the workplace. I’m forced to listen to this rhetoric because my shift isn’t done yet, and I can’t leave without getting fired. I’m forced into a sexual discussion without consent, and it’s so graphically disgusting that I feel nauseous.
The phrase “we’re trying for a baby” communicates the intent to start a family without eliciting unwanted images of raw dog cream pies. That is why we use it. If you are having these thoughts about your coworkers from this phrase, I submit that you are the problem.