Background: it is estimated that approximately 30% to 40% of implanted pregnancies resulted in spontaneous abortion during the first trimester, most of which occur in very early stage. Significant number of losses predominantly occurs very early in gestation, but once the embryonic heart activity appears the rate of spontaneous abortion gradually decreases to 2-5% . Methods: the present study was conducted  at the Department of Obstetrics and Gynecology,6october Hospital during the period between February 2020 and august 2020 .46 cases at 5 weeks of pregnancy were subjected to transvaginal ultrasound  and yolk sac size and  shape were determined .  Records of pregnant women were registered at 6, 9, 12 weeks of pregnancy. Aim Of The Work: to evaluate the value of yolk sac in prediction of pregnancy outcome . Results: Abnormal Shape of yolk sac was found in 11 cases, the mean YSD at 6 weeks in aborted cases was 3.5±1.8 and cases who continued pregnancy was 2.2 ±0.4 and this difference is statistically significant and cut off point at 6 weeks was 2.8 while there was no significant difference between  YSD in  aborted cases and in those who continued pregnancy at 9,12 weeks respectively.  Conclusion: large size of yolk sac at 6 weeks of pregnancy and abnormal shape of yolk sac are predictor of poor pregnancy outcome.