Pregnancy is a high risk period for thrombosis in women with antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) with antiphospholipid antibodies (aPL). Thrombosis may affect the mother, both in the venous and arterial beds, and also have a role in pregnancy loss. Thromboprophylaxis thus is warranted in most of these women. However, specific regimens containing low-dose aspirin, unfractionated heparin (UH), low molecular weight heparin (LMWH), and even dicumarinics in some circumstances after the first trimester are still a matter of controversy. Women with previous thrombosis should receive full antithrombotic doses of UH or LMWH during the whole pregnancy. Treatment of pregnancy losses is more debated, consisting of low-dose aspirin with or without associated heparin. The choice of treatment for a given patient must always take into account the woman's opinion after a careful discussion with the treating physician. Peripartum thromboprophylaxis with LMWH in women receiving aspirin-only regimens and prevention of osteoporosis in those treated with heparin are considered essential in the medical management of these patients.