356: Current practices in determining amnionicity and chorionicity in multiple gestation


      Accuracy of diagnosis of amnionicity and chorionicity (A/C) is vital in the counseling and management of multi-fetal gestations. The purpose of this study was to evaluate the accuracy of A/C diagnoses of referral physicians and a tertiary care center as compared to final histopathologic diagnosis.

      Study Design

      A retrospective cohort study of patients with multi-fetal gestations was performed comparing A/C diagnoses of referring physicians, a tertiary care center, and final histopathology.


      A total of 271 multi-fetal pregnancies were referred for evaluation. Tertiary care center A/C diagnosis was significantly more accurate (p<0.001) than referral physician A/C diagnosis for twin gestations when compared to histopathologic diagnosis. Of 234 referred twin pregnancies, 104 (44.4%) had not been assigned a diagnosis of A/C; 110 (47.0%) had accurately identified A/C prior to tertiary care center evaluation. The tertiary care center accurately identified 227 (97.0%) of the 234 referred twin pregnancies. In the 37 higher order multiples, there was a significant difference (p<0.001) in accuracy of diagnosis when comparing tertiary care center and referral diagnoses to histopathologic diagnosis, when including unassigned patients as an “inaccurate” diagnosis. However there was no significant difference (p=0.5659) when they were excluded from the analysis.


      The accurate diagnosis of A/C can be a complex process that significantly alters pregnancy management. Given the significant differences in accuracy in determining A/C between the tertiary care center and referral physicians, there should be an emphasis on enhancing these diagnostic skills in the general community.