I had to search back to find my post here
We did have identical twins. 2 sacs but sharing the placenta. One never took off after 6 wks, (small shadow seen in the sac at 5w4d) and the other had a heart beat at 6w3d and 7w5d but no heartbeat at 9w1d. I had a D&C last week.
There was also a subchorionic bleed under the portion of the placenta under the twin with the heartbeat. I don't think either of them stood a chance.