BACKGROUND Venous thrombotic events still remain the leading cause of maternal morbidity and mortality. During pregnancy as well as post partum, hemostasis changes also in normal pregnant women. Coagulation is activated and fibrinolysis suppressed, the concentration of particular coagulation factors is increased, while inhibitor potential is decreased. Additionally, the venous blood stream is mechanically hampered by the gravid uterus. As a result of these physiologic changes, the risk of thromboembolism is elevated. The risk increases frequently in women with previous thromboembolic episodes, a family history of thromboembolism, hereditary or acquired thrombotic disorders as well as the appearance of additional exposure prothrombogenic factors such as immobilization, inflammation, and operation. Simultaneous presence of combined prothrombogenic factors conducts a potentiation of the risk of thromboembolism. To avoid thromboembolism or rethromboembolism during pregnancy or puerperium, an individual risk-adapted heparin prophylaxis is indicated. METHODS 17 pregnant women with inherited and/or acquired prothrombogenic disorders, eleven of them with previous thromboembolism episodes, were treated with low molecular weight heparin (LMWH; dalteparin-Na). The daily dose of 5,000-10,000 IU LMWH was applied subcutaneously by self-injection during pregnancy and up to 8 weeks post partum. Every 4 weeks clinical and laboratory monitoring was performed. Basic parameters as well as the special coagulation marker TAT (thrombin-antithrombin complex) and D-dimer were analyzed. RESULTS Under the therapy with LMWH (dalteparin-Na), no thromboembolic events during pregnancy or post partum could be observed. No serious bleeding complications, except small subcutaneous local hematomas, occurred. Bolus applications of LMWH by self-injection were easy to practice, gained a good acceptance and high compliance. Increased TAT values above normal at the actual state of pregnancy could be suppressed to normal values by raising the LMWH dose. CONCLUSIONS The individual thromboembolic prophylaxis with LMWH represents an effective and safe therapy in risk pregnancy with previous thromboembolic events and/or thrombotic disorders. TAT seems to be an effective marker for monitoring of the coagulation activity during pregnancy and puerperium. Under this management, thromboembolic prophylaxis can be optimized.