Antiphospholipi syndrome (APS or APLS) or antiphospholipid antibody syndrome is a disorder of coagulation, which causes blood clots (thrombosis) in both arteries and veins, as well as pregnancy-related complications such as miscarriage, preterm delivery, or severe preeclampsia. The syndrome occurs due to the autoimmune production of antibodies against phospholipid (aPL), a cell membrane substance. In particular, the disease is characterised by antibodies against cardiolipin (anti-cardiolipin antibodies) and β2 glycoprotein I.