Definitely surprising seeings the chance of identical twins is so low (2% or something like that I think?).
I'm going to wait until I see my OB on Friday before making an appointment at the local radiology clinic. She has a pretty high-tech U/S set up in her offices so may be able to see more than FS. FS just has one of those tiny little portable set ups in her office which she did say is just for HB/measurement purposes - not looking at little details. She doesn't seem to think it's a problem at all though, she's just curious to see if it is what she thinks it is. It kind of makes me wonder though about the strong feeling of "something wrong" that I had a few of days off 6wks that prompted me to get a BT through my GP. Could just be pure coincidence, but who knows.