Posting this in case it will help someone else. I had a week plus wait after passing first "Blob" of tissue during my miscarriage until I could get to the doctor to confirm. We had been advised by the ER to keep any large tissues if we wanted to do testing. I believe I passed the sac Wednesday while I was out of town for work and literally wrapped it up as best as I could and took it home on the plane. When I went to the doctor on Friday she asked me if I had kept it in water! So, if you want to do testing, call your doctor and find out the best way to preserve. I am trying to do testing, but I may not ultimately get any results. Will know in 4-6 weeks.