[Thrombophilia, preeclampsia and other pregnancy complications].Acta Med Croatica. 2009 Oct; 63(4):297-305.AM
The aim of this paper is to present the latest developments in therapy and prophylaxis of deep vein thrombosis and other pregnancy complications in women with inherited or acquired thrombophilia and in women with mechanical heart valves. The data presented in the paper have been extracted from the Current Contents database. It is well known that the hypercoagulable state in pregnant women, caused either by the physiological changes of pregnancy or by inherited thrombophilia, increases the risk of venous thromboembolism (VTE), pulmonary embolism (PE), preeclampsia, recurrent early and late fetal loss, intrauterine growth retardation (IUGR), placental abruption, and other less probable complications of pregnancy and its outcome. In women with mechanical heart valves, the risk of systemic embolism is also seen to increase during pregnancy. According to data analyzed, positive antiphospholipid antibodies (APLA) as well as anticardiolipin antibody and lupus anticoagulant (nonspecific inhibitor) positivity, homozygosity and heterozygosity for factor V Leiden mutation and heterozygosity for the prothrombin G20210A variant, MTHFR C677T variant homozygosity and hyperhomocysteinemia are in strong association with pregnancy complications and severe pregnancy outcome. The strongest association for late fetal loss was seen in women with protein S deficiency. In order to reduce such risks, anticoagulation therapy is administered throughout pregnancy. The antithrombotic agents available for the prevention and treatment of VTE during pregnancy and pregnancy complications include unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) and aspirin. Vitamin K antagonists are contraindicated in pregnancy. Low-dose aspirin may have a role in the prevention of some pregnancy complications, although its safety in early pregnancy is uncertain. LMWH and UFH are quite safe and efficacious when properly selected, dosed and monitored. The efficacy and safety of LMWH have been demonstrated in the prevention and treatment of VTE in pregnancy. LMWH in association with aspirin administered throughout pregnancy have been shown to be associated with a lower risk of complications in women with APLA syndrome. Women at a high risk of preeclampsia are recommended to use low-dose aspirin throughout pregnancy. When there is a history of preeclampsia, the administration of anticoagulation therapy is not recommended as a prophylaxis in subsequent pregnancies, as the risk appears to be already decreased as compared with previous pregnancy. LMWH has probable advantages over UFH for the incidence of side effects. In pregnant women with mechanical heart valves, anticoagulant therapy during pregnancy should include assessment of additional risk factors for thromboembolism including valve type, position, and history of thromboembolism, and decision should also be strongly influenced by the patient's preferences. If the risk of thromboembolism in patients with mechanical heart valves is considered very high, and efficacy or safety of prophylaxis with UFH or LMWH is not satisfactory (older-generation prosthesis in the mitral position or history of thromboembolism), administration of vitamin K antagonists throughout pregnancy is recommended with replacement by UFH or LMWH close to delivery. It should be considered that limited effectiveness of UFH or LMWH in patients with mechanical heart valves might be due to inadequate dosing. The necessity of anticoagulation therapy in women with inherited or acquired thrombophilia is biologically plausible; nevertheless, optimum management in such cases remains unknown.