This study was conducted to investigate the effectiveness of serum levels of free beta-hCG, progesterone, CA125 and their combined use in the prediction of first trimester abortions. A total of 140 singleton pregnant women between 5 and 13 weeks' gestational age were included as Group I (n = 21) who resulted in abortion including missed abortion, incomplete abortion, complete abortion and inevitable abortion; Group II (n = 129) included normal pregnancies. When using the free beta-hCG level of <20 ng/ml as a cut off point, the sensitivity, specificity, PPV and NPV were 91%, 82%, 46% and 98%, when using a progesterone of <15 ng/ml as a cut off point, they were 91%, 89%, 59%, 98%. The single measurement of free beta-hCG or progesterone levels can be useful in the prediction of first trimester spontaneous abortions, but using progesterone may be recommended since it has high availability and low cost.