Preeclampsia (PE) complicates 2-8% of pregnancies. It is associated with an increased risk of adverse maternal (death, eclampsia, abruptio placenta, HELLP syndrome) and perinatal (perinatal death, growth restriction, prematurity) outcomes. The only definite treatment of PE remains pregnancy termination. Therefore, prevention of PE remains an important challenge. Low dose aspirin may be used in the prevention of PE, particularly in women who had a severe preeclampsia before 34 weeks. Its efficiency, however, is very weak. Recently, it has been suggested that low molecular weight heparin might be useful in the prevention of PE.