Yolk sac diameter and shape at endovaginal US: predictors of pregnancy outcome in the first trimester.

Abstract

Four hundred eighty-six consecutive women who underwent endovaginal sonography when their fetuses were less than 10 weeks menstrual age (MA) were evaluated to establish the normal size and shape of the secondary yolk sac (YS) and to assess the value of YS measurement in predicting pregnancy outcome in the first trimester. A YS diameter more than two standard deviations (SDs) above the mean when compared with the mean gestational sac diameter allowed prediction of an abnormal pregnancy outcome with a sensitivity of 15.6%, a specificity of 97.4%, and a positive predictive value of 60.0%. A YS diameter more than two SDs below the mean allowed prediction of an abnormal outcome with a sensitivity of 15.6%, a specificity of 95.3%, and a positive predictive value of 44.4%. No pregnancy with a normal outcome had a YS diameter of greater than 5.6 mm at less than 10 weeks MA. In six patients, the YS diameter was greater than 5.6 mm. All six had an abnormal outcome. Of seven patients with abnormal YS shape at initial sonography, three had abnormal YS shape at follow-up examinations. All three had an abnormal outcome.

Correlation analysis between ultrasound findings and abnormal karyotypes in the embryos from early pregnancy loss after in vitro fertilization-embryo transfer

“…The size of the gestational sac was calculated based on the average of three measurements of its perpendicular diameter using calipers placed at the inner edges of the trophoblast [21]. The size of the yolk sac was calculated based on the average of three measurements of its perpendicular diameter relative to the center of the yolk sac wall [22].…”

“…The size of the yolk sac was calculated based on the average of three measurements of its perpendicular diameter relative to the center of the yolk sac wall [22]. The length of the embryonic pole was measured along the anterior to posterior axis [21,23]. The embryonic heart rate was measured from frozen M-mode images using electronic calipers [24].…”

Early Detection of Fetal Abnormality

“…Several reports described that abnormal size of yolk sac was significant in the subsequent spontaneous abortion. [11][12][13][14] In early pregnancy, when huge yolk sac is observed, embryonal demise may occur within several days. Figure 1 shows a huge yolk sac beside an embryo with normal heartbeat.…”

Evaluation of Early Pregnancy Failure with Ultrasound

“…There is a 60% positive predictive value of abnormal pregnancy outcome when the YS is greater than 2 standard deviations above the mean sac diameter. 24,25 However, a large YS is, in general, considered a nonspecific finding with early pregnancy failure. 25 …”