I am 8 weeks pregnant with mono-di twins. I had an ultrasound yesterday at a MFM. Both babies measure exactly 8 weeks, 0 days (which is exactly what I was), and they both had great heartbeats. But baby B had a large yolk sac, and the high risk doctor came in and explained that this usually means an abnormal chromosomal/genetics makeup in the baby and that I will probably miscarry. I have done some research and haven't found too many success stories about this. Anyone have any experience with a large yolk sac with a fetus measuring good and a good heartbeat? Also, they are making me wait three weeks to come back in for another ultrasound, which I think is crazy.