Summary Introduction: It is currently believed that disturbances of maternal clothing system leading to occurrence of thrombotic abnormalities, conditioned by the presence of acquired or inherited thrombophilias, may be an important reason for recurrent abortions. The aim of this study was to investigate frequency and significance of polymorphisms in genes coding for factor V (1691G>A) and factor II (20210G>A) of coagulation cascade in a group of women with two or more miscarriages in the first trimester of pregnancy. Material and methods: The investigations were conducted in a group of 104 women with anamese history of two or more miscarriages in the first trimester of pregnancy and in a group of 169 women with correct obstetrical anamnesis and confirmed presence of at least one pregnancy that resulted in a birth of a healthy child. The analysis was performed by polymerase chain reaction and restriction fragment length polymorphism (PCR/RFLP). Results: Investigation of 20210G>A polymorphism of prothrombin gene revealed high overrepresentation of genotype GA (8.33% and 1,18% in the control group, p=0.07) and allele A (4.17% and 0,59% in the control group, p=0.07) in the subgroup of women with three or more miscarriages. Investigation of 1691 G>A polymorphism showed preponderance of genotype GA (12.50% vs 6,51% , p=0.31) and allele A (6.25% vs 3.25% , p=0,31) in a group of women with miscarriages between 10 and 13 week of gestation in comparison to the control group. Investigation of 20210G>A polymorphism showed majority of genotype GA (8.70%) in women with miscarriages in the early as well as in the late period of the first trimester in comparison to the control group (1.18%, p=0.07). The frequency of occurrance of mutated allele A was 4.35% and 0.59% in the control group (1.18%, p=0.07). Conclusions: The analysis of obtained results suggests the possible influence of both considered polymorphisms 1691G>A of factor V gene and 20210G>A prothrombin gene on mechanism of recurrent miscarriages in the first trimester of pregnancy and participation of 1691G>A polymorphism in the etiology of recurrent miscarriages during the late period of the first trimester of pregnancy (10-13 week of gestation).