PROBLEM: Recently, evidence has accumulated for the presence of the kallikrein–kinin system or plasma contact system in the fetoplacental unit. The Kallikrein–kinin system or plasma contact system consists of three essential plasma proteins. These are coagulation factor XII, prekallikrein and high molecular weight kininogen. Deficiencies of these proteins and antiphospholipid antibodies are frequent hemostasis-related abnormalities found in unexplained recurrent aborters.
METHOD OF STUDY: Review of existing data.
RESULTS: Reports of antiphosphatidylethanolamine antibodies (aPE) with similar or identical pathogenic associations as those described for anticardiolipin antibodies (aCL) are found in the literature. We showed a strong association between recurrent pregnancy losses and aPE, the latter of which recognizes kininogens, and kininogen-binding proteins, factor XI and prekallikrein. The reports of aPE are reviewed, the function of the kininogens are summarized, and their role in pregnancy is discussed.
CONCLUSIONS: Because kallikrein–kinin system may play an important role in pregnancy especially in fetoplacental unit, disruption of this system may be a risk factor for early gestational losses.