title: Further observations on the empty "amnion sign".
abstract: OBJECTIVE
  To assess the positive predictive value of the empty "amnion sign" (visualization of an amnion without concomitant visualization of an embryo) for the diagnosis of early pregnancy failure.
  
  
  METHODS
  Retrospective study of 882 1st trimester sonographic examinations with abnormal findings among women who were threatening to abort. Eight hundred six met the inclusion criteria.
  
  
  RESULTS
  In the study cohort 286 (35.5%) had no identifiable embryo and 71 of those without an identifiable embryo had a visible amnion (24.8%). The breakdown of the mean sac diameter of the study cohort was as follows: those measuring less than 16 mm (n = 16); those measuring 16-20 mm (n = 20); those measuring 21 mm or more (n = 35). Sixty-eight of the 71 patients had adequate follow-up. Pregnancy failure was confirmed in all 68 patients (positive predictive value = 100%).
  
  
  CONCLUSIONS
  The data from this study indicate that visualization of an amnion without concomitant visualization of an embryo (the empty "amnion sign") confirms pregnancy failure regardless of the mean sac diameter and with a sufficiently high positive predictive value to make a definitive diagnosis.
authors.affiliation: Department of Radiology, University of California, San Francisco, L374, 505 Parnassus Avenue, San Francisco, CA 94143-0628, USA.
authors.forename: N Tugce
authors.initials: NT
authors.lastname: Yegul
authors.forename: Roy A
authors.initials: RA
authors.lastname: Filly
mesh_terms: D000650:Amnion / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D020964:Embryo Loss / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*