Three-dimensional measurement of gestational and yolk sac volumes as predictors of pregnancy outcome in the first trimester

Along with crown-rump length (CRL), the size (diameter) of embryonic struct ures such as gestational sac (CS) and yolk sac (YS) may have prognostic val ue for embryonic development. We proposed that first-trimester volume calcu lations of these structures using transvaginal three-dimensional ultrasound technique may have value as predictors of adverse reproductive outcome. Fo rty-nine consecutive patients (treated for infertility) with singleton preg nancies were included in this prospective study. Seventy-three examinations were performed in case of pregnancies with normal, and 12 with abnormal ou tcome. GS and YS volumes were plotted against gestational age (CA) (25-65 d ays post ovulation) to create nomograms for normal outcome and the same pro cedure was carried out with CRL measurements as well. Measurements of abnor mal pregnancies were compared with these nomograms. Specificity sensitivity , positive and negative predictive values were also calculated. Regression analysis revealed a power correlation between GS volumes and GA, logarithmi c relationship was observed when YS volumes were plotted against GA. CRL sh owed logarithmic correlation with CA as well. Both GS volumetry and CRL mea surements proved to have statistically significant predictive value for adv erse outcome (p <0.05). However, no statistically significant difference wa s found when YS volumes of normal and abnormal pregnancies were compared. S pecificity, sensitivity, positive and negative predictive values of GS volu mes and CRL were similar. Mean YS/GS ratios also had good predictive values (P <0.05). Volume determination of YS and GS can be performed quickly and simply applying three-dimensional sonography. Volumetry of GS proved to be a sensitive predictor for pregnancy outcome and can be a good supplement to CRL measurements.