ACCURACY OF PRENATAL SONOGRAPHY FOR DETECTING CIRCUMVALLATE PLACENTA

OBJECTIVE. We determined the accuracy of prenatal sonography for detec ting placental circumvallation, a placental abnormality associated wit h increased fetal morbidity and mortality. MATERIALS AND METHODS. We a nalyzed 62 healthy pregnant (range, 18-36 weeks) patients with focused placental sonography for detection of morphologic abnormality using t he published criteria for circumvallate placenta (irregular edge: upli fted margin, or placental sheet or shelf). Placental marginal sonogram s were taken at 30 degrees intervals around the entire placental margi n, Five experienced sonologists who were unaware of the pathologic fin dings independently reviewed the placental images and graded the place ntas from I (definitely normal) to 5 (definitely circumvallate). Recei ver operating characteristic (ROC) curves and area under the ROC curve were calculated for each reader, Gross and microscopic pathology was used as the gold standard for all cases. RESULTS. In the 62 patients, sonography revealed 49 normal placentas (79%), 12 partially circumvall ate placentas (19%), and one completely circumvallate placenta (2%), R OC curves for the reviewers resulted in values for area under the curv e ranging from .39 to .58, The sonologist who achieved the highest val ue for the area under the curve classified the 13 cases of proven circ umvallation as one case of definite circumvallation, four cases as unc ertain or equivocal, and eight cases as probably or definitely normal placentas, Of the normal placentas, 35% were graded as probably or def initely circumvallate by at least one sonologist. All sonologists misg raded the case of complete circumvallation as normal, CONCLUSION. Focu sed placental sonograms interpreted by experienced sonologists fail to detect the placental edge abnormality in most cases of circumvallatio n. In our study, 17 of 49 normal placentas were diagnosed as probably or definitely circumvallate by one or more observers, Our sonologists' interpretations of sonograms showed that complete circumvallation was difficult to assess, Although our study had a limited number of patie nts, the accuracy of sonography of the placenta for revealing circumva llation appears to be limited.