Hey kezza,
They seem to think it is TTTS hench why 1 is bigger then the other but they don't want to rule out down's so have suggested an amniocentesis. They have said it is up to us weather or not to do it. Im not sure what to do my husband want me to do it because they are twins I think I might do it due to piece of mind I will have to give my answer soon by 16wks. I will have to do a scan every 2 weeks for the TTTS, I have been reading up on TTTS and know alot more about it which is good and bad. I am trying to stay positive at the moment, I did get to see them today and they were moving around alot that was great to see and easied my nervous abit.
It all a big waiting game now.