The immune system protects the body from foreign cells. Lymphocytes and antibodies are responsible for responding to viruses, bacteria, parasites, etc. Sometimes the immune system fails and attacks the cells themselves, talk of autoimmune diseases. In pregnancy happens only something the immune system of the mother accepts the foreign cells of the embryo without attacking. When the rejects and attacks an abortion occurs. The antiphospholipid syndrome is the only autoimmune disorder that accounts for 15% of diagnoses of recurrent abortion and untreated patients are at risk of abortion after the diagnosis of 90%.