The aim of this work was to investigate the relationship between serum progesterone and CA-125 distinguishing successful from unsuccessful pregnancies during the first trimester. The study being a clinical trial included 40 cases of confirmed intrauterine pregnancies between 6-12 weeks with demonstrable embryonic pulsation complicated with vaginal bleeding who were selected from Obstetrics and Gynecology Clinic in Cairo University Hospitals; 20 asymptomatic first trimesteric pregnancy (group 1) and 20 consecutive patients with vaginal bleeding and evidence of embryonic cardiac activity (group 2). Women with blighted ovum or twinning gestation, ectopic pregnancy, and conception by assisted reproductive techniques and those not available to be contacted for follow-up were excluded in the study. Each case in the study were subjected detailed obstetric and gynecological history, clinical examination, determination of gestational age, transvagianl ultrasound examination and measurement of serum CA- 125 and progesterone levels. The values of progesterone and serum CA- 125 were compared between the control group and the study group.