Yolk sac size and shape as predictors of poor pregnancy outcome

Two hundred and fifty women, underwent endovaginal sonography in the first trimester to establish the normal size and shape of the secondary yolk sac and to assess the value of yolk sac evaluation in predicting poor pregnancy outcome. We calculated the correlation coefficients between yolk sac and menstrual age, yolk sac and crown-rump length and between yolk sac and mean gestational yolk sac diameter as r: 0.9581 (p < 0.001), r: 0.9427 (p < 0.0001) and r: 0.8855 (p < 0.0001), respectively. Of 250 cases, 219 had a normal pregnancy course through the end of the first trimester (Group I) while 31 had a poor prognosis such as abortion or embryonic demise (Group II). Eight of 219 in Group I and 20 of 31 in Group II had an abnormal yolk sac size. A yolk sac diameter out of two standard deviations of the mean for the menstrual age allowed prediction of an abnormal pregnancy outcome with a sensitivity of 65%, a specificity of 97%, a positive predictive value of 71%, and a negative predictive value of 95%. Ten of 219 and 9 of 31 had abnormal yolk sac shape. An abnormal yolk sac shape allowed prediction of an abnormal pregnancy outcome with a sensitivity of 29%, a specificity of 95%, a positive predictive value of 47% and a negative predictive value of 90.5%. We concluded that secondary yolk sac evaluation is a valuable tool to predict pregnancy outcome.