Nonviable twin

Has anyone had a nonviable twin in the same gestational sac? I found out almost 4 weeks ago that I had a mass and they gave me possibilities what it could be. I had another ultrasound last weekend and it was still there. I don't see my dr for another 2 weeks to find out what could be going on. I felt like I didn't get all the information from the emergency room which I had my first ultrasound so I requested all of my records. I read that it was a nonviable twin. I was just wondering if anyone had this happen with them and what the outcome was. I have been waiting too long to find out and it's stressful. I'm trying my best not to stress but it's hard.