Mechanisms of pregnancy loss in antiphospholipid syndrome.

Antiphospholipid antibodies are associated with intrauterine fetal growth retardation and fetal distress leading to premature birth or fetal death. These complications are caused by uteroplacental insufficiency that is the result of multiple placental thromboses, infarcts, and spiral artery vasculopathy, which are almost certainly provoked by the hypercoagulable state induced by aPL antibodies. Available data indicate that the thrombogenic function of aPL antibodies involves their general effect on platelets, endothelial cells, anticoagulant mechanisms, and fibrinolytic pathways, as well as their local effect on trophoblasts and villi cells, leading to reduction of annexin V (placental anticoagulant protein-I) production and inhibition of its anticoagulant function.