Introduction:Miscarriage is a common complication of pregnancy occurring in 15% to 20% of all clinically recognized pregnancies. In many cases, the cause of miscarriage cannot be identified; however, among the recognized risk factors of miscarriage are maternal age over 34 years and paternal age over 40 years, previous history of two or more miscarriages, and maternal autoimmune factors.Aim of the study: Maternal serum differential leucocytic count and high-sensitivity C-reactive protein (HSCRP) were evaluated in predicting spontaneous abortion in spontaneous pregnancies presenting with threatened spontaneous abortion.Subjects and methods: 100 pregnant women were divided into two equal groups: the threatened abortion group and the control group. Results:The mean values of WBCs, neutrophils, monocytes, and lymphocytes were significantly higher in the study group. Comparing the level of High sensitivity CRP among the studied groups showed the higher significant mean values of the high sensitivity-CRP in the sera of the study group than in the control group. Conclusion:The current study recommends that increased serum levels of total and differential leucocytic count and serum levels of High sensitivity-CRP are the possible mechanisms involved in the first trimester threatened miscarriage