Antiphospholipid syndrome is an autoimmune
disorder characterized by the presence of specified
levels of antiphospholipid antibodies and one or more
clinical features, including pregnancy loss, thrombosis,
or autoimmune thrombocytopenia. The histologic
findings of placental infarction, necrosis, and
vascular thrombosis in some cases of pregnancy loss
associated with antiphospholipid antibodies have led
to the hypothesis that thrombosis in the uteroplacental
circulation may lead to placental infarction and
ultimately, pregnancy loss (Fig. 1). Numerous retrospective
and prospective studies have linked recurrent
pregnancy loss, especially fetal death, with antiphospholipid
syndrome. The two best
characterized antiphospholipid antibodies are lupus
anticoagulant and anticardiolipin antibodies.