Anti–β 2-glycoprotein I antibodies in women with recurrent spontaneous abortion, unexplained fetal death, and antiphospholipid syndrome

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Objective: Studies in rheumatologic and hematologic populations suggest that anti–β 2-glycoprotein I antibodies are more specific for the clinical manifestations of antiphospholipid syndrome than anticardiolipin antibodies. However, the association between anti–β 2-glycoprotein I and pregnancy loss remains uncertain. We sought to determine whether anti–β 2-glycoprotein I is associated with the obstetric features of antiphospholipid syndrome. Study Design: Sera from 4 groups of women were studied: (1) 152 healthy fertile control subjects, (2) 141 subjects with unexplained recurrent spontaneous abortions, (3) 58 subjects with unexplained fetal deaths, and (4) 73 subjects with well-characterized antiphospholipid syndrome. Serum anticardiolipin and anti–β 2-glycoprotein I levels were determined by enzyme-linked immunoassay. Results: Patients with antiphospholipid syndrome had significantly higher levels of immunoglobulin G and immunoglobulin M anticardiolipin and anti–β 2-glycoprotein I than the other 3 groups ( P < .0001). However, women in the recurrent spontaneous abortion, fetal death, and fertile control groups had similar levels of each antibody. Similarly, there were no differences in the proportion of women with positive test results for each autoantibody in these 3 groups. Linear regression analysis showed significant correlation between anticardiolipin immunoglobulin G and β 2-glycoprotein I immunoglobulin G ( R 2 = 0.544786, P = .0001) and anticardiolipin immunoglobulin M and β 2-glycoprotein I immunoglobulin M ( R 2 = 0.525048, P = .0001). Conclusion: Both anticardiolipin and anti–β 2-glycoprotein I are associated with antiphospholipid syndrome. However, testing for anti–β 2-glycoprotein I does not identify additional patients with either recurrent spontaneous abortions or unexplained fetal deaths who initially have negative test responses for anticardiolipin. This is likely because of the strong correlation between the 2 autoantibodies. Our data do not support routine testing for anti–β 2-glycoprotein I in addition to testing for antiphospholipid antibodies in women with recurrent pregnancy loss and unexplained fetal death. (Am J Obstet Gynecol 1999;181:642-8.)