Thromboembolic events are among the leading causes of maternal mortality. Mutations in the genes for clotting factors are known, but anamnestic factors can be found in a proportion of women with deep venous thromboses (DVT) during pregnancy and the puerperium. We here describe the clinical factors and pregnancy outcomes of such a group of 70 women who were all operated on for DVT. Highest risk is conferred by a familial history of clotting disease and by known mutations of the clotting factors. This might be used to target a high risk group for preventive treatment.