Introduction: Early pregnancy loss is the most common complication of early pregnancy. First trimester is crucial, since 80% of pregnancy losses occur spontaneously during this period. There is great difficulty in reliably anticipating which pregnancies will terminate in abortion. The yolk sac is the first extra embryonic structure that becomes sonographically visible within the gestational sac. Aims and Objectives of the present study is to evaluate the size of yolk sac as a predictor of pregnancy outcome. Material and Methods:The present Observational Prospective study was conducted on 104 pregnant woman with gestational age 6 to 10 weeks attending OPD in the department of obstetrics and gynaecology at MVJ Medical college and research hospital from December 2020 to December 2022 Results: In present study Mean age of the study participants was 25.31+4.483 and mean values of radiological findings were gestational age (days)56.28days ±8.120, MSD was 2.2545±0.99, YSD was 2.25±0.99, CRL was 1.29±0.66 and HR was 156.61±13.453. Majority of the study participants 71.2% had normal perinatal outcome. There is steady increase in YSD mean value and difference observed is statistically significant. Statistically significant differences were observed between normal and abnormal perinatal outcome. Conclusion: Abnormalities of YS size or shape, early regression or absence can be used as poor predictor of first trimester pregnancy outcome, even before studying the fetal morphology.