THE YOLK SAC

 

NORMAL YOLK SAC

 

Link to Normal Yolk Sac.

 

ABNORMAL YOLK SAC
    • Large yolk sac >6mm.
    • Small yolk sac £2mm (1).
    • Irregular shape.
    • Calcified yolk sac - due to longstanding embryonic demise.
    • Floating yolk sac.
    • Solid echodense yolk sac (associated with fetal death or an anomalous fetus) (1).
    • Non visualization is always abnormal.
    • Thin yolk sac - predictive value of 53.8% for an abnormal outcome.(2)
    • Thick yolk sac - predictive value of 93.3% for an abnormal outcome.(2)

 

                       Dense, echogenic yolk sac.                                Echogenic chorionic cavity

Small (1.6 mm) yolk sac with an echogenic chorionic cavity.

Large yolk sac (10.3 X 9.5 mm) at 7 weeks 5 days.

Adjacent fetus seen, but amniotic cavity not yet visible.

 

Large yolk sac:

-         yolk sac 6.6 mm

-         fetal bradycardia 94 bpm

-         demise 1 week later

               Floating Yolk Sac                                               Thin Yolk Sac

 


REFERENCES
  1. Green JJ, Hobbins JC. Abdominal ultrasound examination of the first trimester fetus. Am J Obstet Gynecol 1988,159:165.
  2. Levi CS, Lyons EA, Lindsay DJ. Ultrasound in the first trimester of pregnancy. Radilologic Clinics of North America 1990,28:19-38.
  3. Ferrazzi E, Brambati B, Lanzani A. The yolk sac in early pregnancy failure. Am J Obstet Gynecol 1988;158:137-141.
  4. Recce EA, Scioscia AL, Ointer E. Prognostic significance of the human yolk sac assessed by ultrasonography. Am J Obstet Gynecol 1988;159:191-196.
  5. Kurtz AB, Needleman L, Pennell RG. Can detection of the yolk sac in the first trimester be used to predict the outcome of pregnancy? A prospective sonographic study. Am J Roentgen 1992;158:843-846.