Wow I can't imagine hoping for the best for you and your babies...
They scheduled me for an additional ultrasound may 5th to check the status of what's going on in there. I felt, compared to pregnant coworkers, the mutual untrasound tech we had spent less time on me than them. They went home with eight frames of their babies. I was only sent home with four! My OB ordered the additional upcoming ultrasound I think I will get more answers then!
I knew a couple who had a twin pregnancy and during the 25th week the one twin started taking all the nutrients and the other twin didn't make it. :( but apparently vanishing twin is more common. Hopefully the one is just hiding. Are they gonna send you for more tests or just wait it out?