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J Ultrasound Med. 2009 Oct;28(10):1331-5.

The expanded amnion sign: evidence of early embryonic death.

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  • 1Department of Radiology, University of California, San Francisco, CA 94143-0628 USA.



The purpose of this study was to assess the positive predictive value for confirming early embryonic death in the clinical scenario wherein an embryo is identified without a visible heartbeat, but the embryonic crown-rump length (CRL) is 5 mm or less.


We conducted a retrospective study of 882 first-trimester sonograms with abnormal findings among women who were threatening to abort. Eight hundred six met the inclusion criteria.


Among the cohort of 806 cases, 520 (64.5%) had an identifiable embryo, and 255 of those with an identifiable embryo had a visible amnion (49.0%). One hundred sixteen of the 255 with a visible amnion and an identifiable embryo without a heartbeat had a CRL that measured 5 mm or less (45.5%). The CRL of these embryos ranged from 1.7 to 5.4 mm (ie, when rounded to the nearest millimeter, these embryos would be 5 mm) with the breakdown as follows: those measuring less than or equal to 3.4 mm (n = 28), those measuring 3.5 to 4.4 mm (n = 45), and those measuring 4.5 to 5.4 mm (n = 43). Eight of these 116 patients did not have any documented follow-up. In the remaining 108 patients, pregnancy failure was confirmed.


We conclude that any embryo that is surrounded by an amnion and that also lacks a heartbeat has unfortunately but definitively died. This is equally true for embryos measuring less than 5 mm in CRL.

[PubMed - indexed for MEDLINE]
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