To establish the prevalence of inherited and acquired risk factors for development of venous thromboembolism (VTE) in pregnancy and the puerperium.In a retrospective study, 30 women with a history of objectively confirmed venous thromboembolism during pregnancy or the puerperium were studied. Fifty-six women with normal pregnancies were included as controls. Antithrombin, protein C, protein S, lupus anticoagulants, homocysteine, factor V Leiden mutation, prothrombin 20210G-->A polymorphism, methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism and the -675 (4G/5G) polymorphism in plasminogen activator inhibitor 1 gene were analysed.At least one thrombophilic defect was observed in 16 (53.3%) cases and in 12 (21.4%) controls (P=0.003); factor V Leiden in 8 (26.7%) cases and 3 (5.7%) controls (P=0.009); prothrombin 20210G-->A polymorphism in 8 (26.7%) cases and 4 (7.5%) controls (P=0.021) and antithrombin deficiency in 4 (13.3%) cases and in 1 (1.8%) control (P=0.029). Other inherited and acquired risk factors were similarly distributed among cases and controls.Women with pregnancy-related venous thromboembolism have an increased prevalence of inheritable thrombophilic defects predisposing them to an increased risk of thrombosis.