In APS patients, the most common venous event is deep vein thrombosis of the lower extremities, and the most common arterial event is stroke. In pregnant person affected by APS, there is an increased risk of recurrent miscarriage, intrauterine growth restriction, and preterm birth. A frequent cause of such complications is placental infarctions. In some cases, APS seems to be the leading cause of intellectual and/or developmental disabilities in the newborn, due to an aPL-induced inhibition of trophoblast differentiation. The antiphospholipid syndrome is responsible for most of the miscarriages in later trimesters seen in concomitant systemic lupus erythematosus and pregnancy.Other common findings, although not part of the APS classification criteria, are low platelet count, heart valve disease, and livedo reticularis. There are also associations between antiphospholipid antibodies and different neurologic manifestations including headache, migraine, epilepsy, and dementia. Some studies have shown the presence of antiphospholipid antibodies in the blood and spinal fluid of patients with psychological symptoms. Cancer is also observed to comorbid in patients with APS. Risk factors
Risk factors for developing antiphospholipid syndrome include:

Genetic Markers: HLA-DR4, HLA-DR7, and HLA-DRw53
Race: Blacks, Hispanics, Asians, and Native Americans

Pathogenesis
Antiphospholipid syndrome is an autoimmune disease, in which "antiphospholipid antibodies" (anticardiolipin antibodies and lupus anticoagulant) react against proteins that bind to anionic phospholipids on plasma membranes. Like many autoimmune diseases, it is more common in women than in men. The exact cause is not known, but activation of the system of coagulation is evident.
Antiphospholipid syndrome, or antiphospholipid antibody syndrome (APS or APLS), is an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS provokes blood clots (thrombosis) in both arteries and veins as well as pregnancy-related complications such as miscarriage, stillbirth, preterm delivery, and severe preeclampsia. Although the exact etiology of APS is still not clear, genetics is believed to play a key role in the development of the disease. The diagnostic criteria require one clinical event (i.e. thrombosis or pregnancy complication) and two positive blood test results spaced at least three months apart that detect lupus anticoagulant, anti-apolipoprotein antibodies, or anti-cardiolipin antibodies.Antiphospholipid syndrome can be primary or secondary. Primary antiphospholipid syndrome occurs in the absence of any other related disease. Secondary antiphospholipid syndrome occurs with other autoimmune diseases, such as systemic lupus erythematosus. In rare cases, APS leads to rapid organ failure due to generalised thrombosis; this is termed "catastrophic antiphospholipid syndrome" (CAPS or Asherson syndrome) and is associated with a high risk of death. Antiphospholipid syndrome often requires treatment with anticoagulant medication such as heparin to reduce the risk of further episodes of thrombosis and improve the prognosis of pregnancy. Warfarin (brand name Coumadin) is not used during pregnancy because it can cross the placenta, unlike heparin, and is teratogenic. Signs and symptoms
The presence of antiphospholipid antibodies (aPL) in the absence of blood clots or pregnancy-related complications does not indicate APS (see below for the diagnosis of APS). Antiphospholipid syndrome can cause arterial or venous blood clots, in any organ system, or pregnancy-related complications.