From 1998 to 2003, 133 Caucasian women aged 17–40 years (median 29 years) suffering from unexplained recurrent miscarriage (uRM) were consecutively enrolled. In patients and 133 age-matched healthy controls prothrombotic risk factors (factor V (FV) G1691A, factor II (FII) G20210A, MTHFR T677T, 4G/5G plasminogen activator inhibitor (PAI)-1, lipoprotein (Lp) (a), protein C (PC), protein S (PS), antithrombin (AT), antiphospholipid/anticardiolipin (APA/ACA) antibodies) as well as associated environmental conditions (smoking and obesity) were investigated. 70 (52.6%) of the patients had at least one prothrombotic risk factor compared with 26 control women (19.5%; p 30 mg/dL, increased APA/ACA and BMI > 25 kg/m2 in combination with a prothrombotic risk factor were found to be significantly associated with uRM. In multivariate analysis, increased Lp(a) (odds ratio (OR): 4.7/95% confidence interval (CI): 2.0–10.7), the FV mutation (OR:3.8/CI:1.4–10.7), and increased APA/ACA (OR: 4.5/CI: 1.1–17.7) had independent associations with uRM.