Antiphospholipid syndrome in pregnancy

Antiphospholipid syndrome (APS) is an autoimmune condition, in which antiphospholipid antibodies (aPL) cause clinical features including thrombosis, fetal loss, and preterm delivery. Studies in large numbers of patients with APS show that they suffer both early and late fetal loss as well as complications of pregnancy such as preeclampsia. The fetal loss in patients with APS is not caused primarily by thrombosis, but by a number of biological effects of aPL that affect implantation of the embryo. These factors are not yet understood fully but include effects on trophoblast cell viability and migration, inflammation at the fetal-maternal interface, and activation of complement. The established management of pregnancy in patients with known obstetric APS is to give daily low-dose oral aspirin plus daily subcutaneous heparin. This gives a live birth rate of over 70%. The trials that led to this form of management being adopted were small but overall do support the use of the heparin/aspirin combination over aspirin alone. There is no definite evidence supporting the use of heparin plus aspirin in patients who are aPL-positive, but who have never suffered any problems in pregnancy. However, patients taking long-term warfarin for thrombotic APS should have this changed to heparin during pregnancy.