Abnormal Sac


I went in for my first ultrasound at 5 weeks and 5 days and was told that I had an abnormal sac and had a 50/50 chance of loosing this pregnancy. This comes after two failed pregnancies. I’m now 6 weeks and 6 days and have another ultrasound Wednesday. I’m just wandering if anyone knows anything about abnormal sacs or has maybe had one that turned out okay?