Immunological disorders:
1. Antiphospholipid syndrome - an autoimmune process in which thrombosis of the vessels of the placental site occurs due to endothelial damage by antibodies to phospholipids of cell membranes. This leads to the emergence of macro- and microthrombi with the involvement of vessels of various caliber and localization. Antiphospholipid antibodies include: lupus anticoagulant, anticardiolipins M and G, etc.
2. Conflict on the ABO system (that is, different blood types for mother and father) or Rh factor, homozygosity of mother and father for the HLA genes (tissue compatibility systems). Pregnancy from an immunological position is an allograft (a transplant obtained from an individual of the same biological species), which has 50% paternal antigens alien to the maternal microorganism. At the same time, the normal course of pregnancy is provided by many protective factors associated with the characteristics of the immunological reactions of the mother's body.