title: Intradecidual sign: is it effective in diagnosis of an early intrauterine pregnancy?
abstract: OBJECTIVE
  To determine if the intradecidual sign at sonography is effective in the diagnosis of early intrauterine pregnancy.
  
  
  METHODS
  In 102 pregnant patients, transvaginal sonography revealed an intrauterine fluid collection without a yolk sac or embryo. Four observers (experienced sonologist, body imaging fellow, 1st-year radiology resident, and premedical student) determined independently whether the intradecidual sign was absent, present, or indeterminate. Interpretations were limited to visualization of only the uterus.
  
  
  RESULTS
  Follow-up revealed intrauterine pregnancy in 91 patients (outcome normal in 48 and abnormal in 43) and ectopic pregnancy in 11 patients. Among the four reviewers, sensitivity for diagnosis of an intrauterine pregnancy was 34%-66%, specificity was 55%-73%, accuracy was 38%-65%, positive predictive value was 91%-93%, and negative predictive value was 12%-16%. Three to five ectopic pregnancies were categorized incorrectly as demonstrating the intradecidual sign, depending on the reviewer.
  
  
  CONCLUSIONS
  The intradecidual sign does not appear to be sensitive or specific in diagnosis of an early intrauterine pregnancy. When an intrauterine fluid collection is present without an embryo or yolk sac (with positive pregnancy test results), a follow-up sonogram should be obtained unless contraindicated clinically.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: F C
authors.initials: FC
authors.lastname: Laing
authors.forename: D L
authors.initials: DL
authors.lastname: Brown
authors.forename: J F
authors.initials: JF
authors.lastname: Price
authors.forename: S
authors.initials: S
authors.lastname: Teeger
authors.forename: M L
authors.initials: ML
authors.lastname: Wong
mesh_terms: D003656:Decidua / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005321:Extraembryonic Membranes / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D014599:Uterus / Q000000981:diagnostic imaging*