OC023: is the Appearance of the Yolk Sac Predictive of Aneuploidy in Early Missed Abortions?

VOCAL TM technique was used to create computerized surface models that were used to characterize gestational sac shapes into one or more of the following groups: disk, spherical, ellipsoid, irregular, and concave. Sac volume changes were analyzed using repeated measures ANOVA. Observer bias and limits of agreement (LOA) for sac volume measurements were examined using Bland-Altman plots. Results: Thirty-three volume datasets were analyzed. Mean menstrual ages were 8.4 ± 0.7 wks (Scan 1); 10.8 ± 0.6 weeks (Scan 2); and 12.8 ± 0.7 weeks (Scan 3). Sac volumes increased by an average of 416 ± 158% over the three visits (p < 0.001). Relative frequencies for gestational sac morphology were: irregular (94%), concave (79%), disk (73%), ellipsoid (21%), and spherical (6%); only two sacs had a single attribute (spherical or ellipsoid). TA and EV sonography yielded similar results with a bias of 1.1 ± 3.1% (95% LOA −4.9 to + 7.1%). For EV sac volumes, the results were: intraobserver −1.4 ± 4.8% (95% LOA −10.8 to + 8.1%); interobserver −4.8 ± 6.4% (95% LOA −17.4 ± 7.8%). The ellipsoid model consistently overestimated EV sac volumes obtained by VOCAL TM −100 ± 19.9% (95% LOA −139 to −61%). Conclusions: Early gestational sacs commonly appear as irregular disk-like structures with a concave surface caused by the placenta. These observations may have significant implications for the accuracy of sac volume measurements. Reproducible results can be rapidly obtained using VOCAL TM from either TA or EV approaches. Morphologic and quantitative analysis of the gestational sac provide baseline parameters to study patients at risk for early pregnancy failure.