Antiphospholipid syndrome (APS) is a rare condition clinically characterized by thrombotic events or pregnancy complications and confirmed by one or more repeatedly positive anti-phospholipid antibodies on two or more occasions at least 12 weeks apart. Several factors are thought to have roles in the pathogenesis of adverse obstetric events related to APS, including platelet and endothelial cell activation, complement activation, and ultimate activation of the thrombotic pathway. Despite standard treatment with a heparin agent and low-dose aspirin, 30% of women with definite APS cannot achieve a successful pregnancy outcome. Additional treatment options are still controversial, and prospective trials with appropriate controls are needed to investigate the efficiency of alternative treatments. In this chapter, we discuss diagnostic, clinical, and therapeutic approaches in the treatment of APS syndrome in pregnancy. (C) 2019 Published by Elsevier Ltd.