Post-partum superficial and deep venous thrombosis are still an important obstetric problem. Varicose veins of the lower limbs are closely associated epidemiologically and pathogenically with venous thrombosis. A controlled group of 1,588 parturients was studied to single out other risk factors and to ascertain the prevalence of thrombosis. A group of 1,464 parturients was treated with graduated compression stockings, in low risk patients, adding preventive treatment with low dose heparin in high risk patients. The prevalence of post-partum venous thrombosis was reduced from 4.3%, in the control group, to 0.9% in the study group: in women who received preventive treatment, the prevalence of thrombosis diseases was decreased over 90%.