How I diagnose and treat antiphospholipid syndrome in pregnancy

Abstract Antiphospholipid syndrome (APS) is a rare autoimmune disease characterized by arterial, venous, or microvascular thrombosis, pregnancy morbidities, or nonthrombotic manifestations in patients with persistently positive antiphospholipid antibodies. These antibodies bind cellular phospholipids and phospholipid–protein complexes resulting in cellular activation and inflammation that lead to the clinical features of APS. Our evolving understanding of APS has resulted in more specific classification criteria. Patients meeting these criteria should be treated during pregnancy according to current guidelines. Yet, despite treatment, those positive for lupus anticoagulant have at least a 30% likelihood of adverse pregnancy outcomes. Patients with recurrent early miscarriage or fetal death in the absence of preeclampsia or placental insufficiency may not meet current classification criteria for APS. Patients with only low titer anticardiolipin or anti–β(2)-glycoprotein I antibodies or immunoglobulin M isotype antibodies will not meet current classification criteria. In such cases, clinicians should implement management plans that balance potential risks and benefits, some of which involve emotional concerns surrounding the patient’s reproductive future. Finally, APS may present in pregnancy or postpartum as a thrombotic microangiopathy, a life-threatening condition that may initially mimic preeclampsia with severe features but requires a very different treatment approach.