Aim: The aim of this study was to estimate the prevalence of factor V Leiden and prothrombin gene G20210A mutation among women with pregnancy loss in Poland. Material and methods: we analyzed a group of 396 women (mean age of 30.4 (±4.6) years), who experienced at least one pregnancy loss. Patients were recruited from 6 academic centers (Poznań, Białystok, Lublin, Wrocław, Bydgoszcz, Gdańsk), and were divided into the following groups: 122 patients with 3 episodes of early recurrent pregnancy loss (group 1), 87 patients with late pregnancy loss (group 2) and 46 patients with intrauterine pregnancy loss (group 3). Patients who did not fulfill the above inclusion criteria were divided into additional groups. 50 healthy women (mean age of 29.2 (±4.5) years), having at least one child, constituted the control group. Factor V Leiden mutation and prothrombin G20210A gene mutation were examined in all 396 women with pregnancy loss and 50 controls. For molecular analysis peripheral blood was tested. Genome DNA isolation from lymphocyte was performed with commercial assay QIAampDNA Blood Mini Kit. Results: Among 396 women with unexplained loss of at least one pregnancy 36 (9.1%) were carriers of inherited thrombophilia. Factor V Leiden mutation was present in 29 women (7.3%), prothrombin gene mutation G20210A in 6 (1.5%) and in 1 (0.3%) patient both mutations were detected. No coagulation defects were found in the control group. Factor V Leiden mutations was the most common disorder (21.7%) in patients with intrauterine demise and was significantly higher than in the group of women with early recurrent and late losses, p<0.011 and p<0.006 respectively. The frequency of G20210A prothrombin gene mutation did not differ substantially between the examined groups; the highest number (2.6%) was found in women with early and late pregnancy losses, and the lowest number (0.8%) was seen in women with early recurrent miscarriages. Conclusion: Factor V Leiden screening should be performed, regardless of negative history of thrombosis, in patients who experienced intrauterine fetal demise or recurrent early miscarriages.