Yolk sac and its effects on fetal prognosis

Sankar Kumar Das, Priyanka Roy


Background: The yolk sac is the first extra embryonic structure that becomes sonographically visible within the gestational sac. It provides nutritional, metabolic, endocrine, immunologic, and hematopoietic functions during organogenesis in embryonic life, before placental circulation is established. Spontaneous abortion rates are significantly elevated where the yolk sac volume falls outside the 5th to 95th percentile. Abnormal morphological appearance of the yolk sac is also suggestive of serious growth disorders of the fetus. The aim is to find out the predictive value of yolk sac on outcome of the pregnancy and any probable relationship of the yolk sac pattern with the gender of the fetus.

Methods: The present study was carried out on fifty patients in their first trimester of pregnancy. Patients were divided into their respective gestational age groups and according to the morphology of the yolk sac. Data were compared using Chi square test. p value less than 0.5 was considered significant.

Results: Out of the fifty patients, twenty-nine were having regular yolk sac, eleven were with irregular yolk sac and ten were with hyperechoic yolk sac. There was a significant number of fetal demise in the cases with hyperechoic and irregular yolk sac. Also, there were hardly any live births in the few cases in which the yolk sac was either too small or too big.

Conclusions: The present study concludes that along with a yolk sac of a given normal range for its size, it should also be of normal morphology for better prognosis of the pregnancy. Also, the increase in the number of female live births needs further studies as to whether there is any abnormality in the Y chromosome causing morphologically abnormal yolk sac and subsequent fetal demise.


First trimester, Pregnancy outcome, Transvaginal sonography, Yolk sac, Yolk sac morphology, Yolk sac size

Full Text:



Pereda J, Niimi G. Embryonic erythropoiesis in human yolk sac: two different compartments for two different processes. Microsc Res Tech. 2008;71:856-62.

Kurtz AB, Needleman L, Pennell RG, Baltarowich O, Vilaro M, Goldberg BB. Can detection of the yolk sac in the first trimester be used to predict the outcome of pregnancy? A prospective sonographic study. AJR Am J Roentgenol. 1992;158:843-7.

Kucuk T, Duru NK, Yenen MC, Dede M, Ergun A, Baser I. Yolk sac size and shape as predictors of poor pregnancy outcome. J Peronat Med. 1999;27:316-20.

Moradan S, Forouzeshfar M. Are abnormal yolk sac characteristics important factors in abortion rates? Int J Fertil Steril.2012;6(2):127-30.

Tan S, Ipek A, Pektas MK, Arifoğlu M, Teber MA, Karaoğlanoğlu M. Irregular yolk sac shape: is it really associated with an increased risk of spontaneous abortion? J Ultrasound Med. 2011;30:31-6.

Lindsay DJ, Lovett IS, Lyons EA. Yolk sac diameter and shape at endovaginal US: predictors of pregnancy outcome in the first trimester. Radiol. 1992;183:115-8.

Chao S, McGahan JP. Yolk sac. In: Goldberg BB, McGahan JP, eds. Atlas of Ultrasound Measurements. 1st ed. Philadelphia, PA: CV Mosby Co; 2006:15-17.

Lyons EA, Levi CS. The first trimester. In: Rumack CM, Wilson SR, Charboneau JW, eds. Diagnostic Ultrasound. 3rd ed. St Louis, MO: CV Mosby Co; 2005:1070-1100.

Harris RD, Vincent LM, Askin FB. Yolk sac calcification: a sonographic finding associated with intrauterine embryonic demise in the first trimester. Radiol. 1988;166:109-10.

Szabo J, Gellén J, Szemere G, Faragó M. Significance of hyper-echogenic yolk sac in first-trimester screening for chromosome aneuploidy [in Hungarian]. Orv Hetil. 1996;137:2313-5.

Tan S, Pektas MK, Arslan H. Sonographic evaluation of the yolk sac. J Ultrasound Med, AIUM. 2012;31(1):87-95.

Adija P, Selvi C, Rai L, Hebbar S. Evaluation of yolk sac diameter and embryonic heart rate as prognostic factors of gestational outcome in early singleton pregnancies. Scholars J App Med Sci (SJAMS). 2015;3(2A):543-50.

Berdahl DM, Blaine J, Van Voorhis B, Dokras A. Detection of enlarged yolk sac on early ultrasound is associated with adverse pregnancy outcomes. Fertil Steril. 2010;94:1535-7.

Cho FN, Chen SN, Tai MH, Yang TL. The quality and size of yolk sac in early pregnancy loss. Aust N Z J Obstet Gynaecol. 2006;46:413-8.

Moradan S, Forouzeshfar MF. Are abnormal yolk sac characteristics important factors in abortion rates?. Int J Fertil Steril. 2012;6(2):127-30.

Levi CS, Lyons EA, Lindsay DJ. Early diagnosis of nonviable pregnancy with endovaginal US. Radiol. 1988;167:383-5.

Tan S, Tangal NG, Kanat-Pektas M, Özcan AŞ, Keskin HL, Akgündüz G, et al. Abnormal sonographic appearances of the yolk sac: which can be associated with adverse perinatal outcome?. Med Ultrason. 2014;16(1):15-20.