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 structures such as gestational sac (GS) and yolk sac (YS) may have prognostic value for embryonic development. We proposed that first-trimester volume calculations of these structures using transvaginal three-dimensional ultrasound technique may have value as predictors of adverse reproductive outcome. Forty-nine consecutive patients (treated for infertility) with singleton pregnancies were included in this prospective study. Seventy-three examinations were performed in case of pregnancies with normal, and 12 with abnormal outcome. GS and YS volumes were plotted against gestational age (GA) (25-65 days post ovulation) to create nomograms for normal outcome and the same procedure was carried out with CRL measurements as well. Measurements of abnormal 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, logarithmic relationship was observed when YS volumes were plotted against GA. CRL showed logarithmic correlation with GA as well. Both GS volumetry and CRL measurements proved to have statistically significant predictive value for adverse outcome (p<0.05). However, no statistically significant difference was found when YS volumes of normal and abnormal pregnancies were compared. Specificity, sensitivity, positive and negative predictive values of GS volumes 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.