Background: Incidence of miscarriage in the first trimester is 80% of all pregnancy losses, this high incidence demands further inquiry to predict early pregnancy outcomes. Thus, using transvaginal sonography, the yolk sac diameter will be assessed as a predictor of the outcome of the first trimester of pregnancy. Therefore, our goal was to assess the reliability of measuring the yolk sac diameter as a predictor of pregnancy outcome in the first trimester.

Methods: This Prospective cohort study was conducted at tertiary care hospital at the ultrasound and fetal medicine unit of the Obstetrics and Gynecology department at Zagazig University Hospitals and Al-Ahrar Teaching Hospital on total 80 patients who presented in their first trimester between 5 to 11 weeks of gestation for antenatal care.

Results: There was a highly significant difference between normal and abnormal yolk sacs regarding 1st-trimester outcome. 54 out of 58 cases with normal yolk sacs had a normal outcome and only 4 had abnormal outcomes. While out of 22 cases with abnormal yolk sacs, 4 women had normal outcomes and 18 abnormal outcomes.

Conclusion: An important, practical, and non-invasive technique for the examination, diagnosis, and follow-up of pregnant women in their early pregnancy is the first trimester ultrasound measurement of the yolk sac diameter, which is taken between weeks 5 and 11. This is helpful when advising expectant mothers about the possibility of an aberrant outcome and the necessity of follow-up ultrasounds.