Sonographic Evaluation of the Yolk Sac

Abstract

This pictorial essay aims to inform related clinicians by summarizing the normal and abnormal sonographic findings of the yolk sac in the first trimester of pregnancy. An abnormality in the sonographic appearance of a yolk sac can predict subsequent embryonic death or abnormalities. Therefore, the accurate recognition of normal and abnormal sonographic findings concerning the yolk sac can be used to anticipate the course of pregnancy.

Efficacy of first‐trimester ultrasound parameters for prediction of early spontaneous abortion

“…concluded that YSD below the 2.5th percentile or above the 97.5th percentile had an odds ratio of 15.86 ( P <0.001) for abortion. Tan et al . reported that YSD more than 1 standard deviation above the mean had a sensitivity of 37.5% for predicting abortion.…”

“…In a study of 188 pregnancies, Wie et al 12 concluded that YSD below the 2.5th percentile or above the 97.5th percentile had an odds ratio of 15.86 (P<0.001) for abortion. Tan et al 18 reported that YSD more than 1 standard deviation above the mean had a sensitivity of 37.5% for predicting abortion. Papaioannou et al 13 reported that if YSD was below the 5th percentile, the chance of abortion would be 8.5% with a false-positive rate of 5%, 13 whereas if it was above the 95th percentile, the chance would be 22.4% with a false-positive rate of 5%.…”

Early sonographic markers and prediction of pregnancy outcome: a prospective study

“…Therefore, the yolk sac is crucial in early embryonic life followed by appearance of embryo and cardiac activity. 3 Normal FHR is~110 bpm (mean) by 5-6 weeks and~170 bpm by 9-10 weeks. This is followed by a decrease in FHR becoming on average: ~150 bpm by 14 weeks,~140 bpm by 20 weeksand.~130 bpm by term.…”

Fetal Biometry in Early Pregnancy

“…As mentioned previously, the YS offers confi rmation of intrauterine pregnancy, and can even help to indicate amnionicity in multiple gestations, as the number of YSs should correlate with the number of amniotic sacs if the embryos are viable [ 8 ]. This can be particularly important in higher order multiple gestations.…”