Anticoagulation during pregnancy should derive benefit from recent advances in anticoagulant therapy. Unfractionated heparin is at present the drug of choice for most of the indications of thromboprophylaxis as well as for acute venous thrombosis during pregnancy but it is likely that, in the near future, low molecular weight heparins will supercede this anticoagulant in many indications. One particular indication is mechanical heart valves that needs a high degree of anticoagulation. The anticoagulant of choice that carries the best efficacy-risk ratio in this situation seems to be oral anticoagulants. Pregnant women receiving anticoagulation should be considered as high-risk patients that should be managed in specialized centres. They are prone to bleeding complications that will mainly occur during delivery or in the postpartum period.