CHORUS
Collaborative Hypertext of Radiology
Pregnancy / Fetus
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gestational sac
arises from blastocyst which implants into secretory endometrium; surrounded by echogenic trophoblast
sac size:
- 6th week = 17mm;
- 8th week = 31 mm
- fills chorionic cavity by 12th week
visualization of gestational sac
- relative to beta-hCG levels:
- transabdominal scan: > 1800 IU/l
- transvaginal scan:
- < 500 IU/l = 20%
- 500-1000 IU/l = 80%
- > 1000 IU/l = 100%
- relative to menstrual age
- transabdominal scan: earliest by 5.5 weeks (10-12mm)
- transvaginal scan: routinely seen by 5-5.5 weeks
see: double decidual sac
Yong H. Hahn, MD - 2 February 1995
Last updated: 1 October 2013
Copyright © 2013, Charles E. Kahn, Jr.
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