Chorionhöhle sollte das heißen - IMO.

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Note added at 26 mins (2010-08-26 15:07:57 GMT)
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See this English descrition:

Early sonographic signs of impending abortion:
- Disruption of the double ring or massive detachment of the gestational sac, with blood behind the placental trophoblast.
- An empty gestational sac >2cm in diameter.
- Bizarre –shaped gestational sac with amorphous blobs.
- A clearly defined foetus devoid of active cardiac activity.

see esp. "bizarre-shaped gestational sac" - that's an attempt for the "Entrundung" part.

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Note added at 27 mins (2010-08-26 15:09:04 GMT)
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sorry, the URL for that part:

http://ohanyido.tripod.com/id12.html