Fluctuations in levels of antiphospholipid antibodies and increased coagulation activation markers in normal andheparin-treated antiphospholipid syndrome pregnancies

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Abstract
Antiphospholipidantibodies (aPL) are associated with anincreased risk of thrombosis and recurrent miscarriage. Weassessed levels of coagulation activation markers and aPL during normal pregnancy and in women with the antiphospholipid syndrome (aPS). Fluctuations in aPL levels were observed in all patients with aPS. No particular pattern of antibody positivity, or fluctuation in aPL level,was associated with poor pregnancy outcome. A significant increase was observed in levels of factor XIIa(FXIIa; P 0.001), factor VIIa (FVIIa, P 0.001), thrombin antithrombin complexes (TAT; P 0.001), prothrombin fragment F1.2 (F1.2; P 0.001) and D-dimer (DD; P 0.05) during normalpregnancy. Factor VIIa, TAT, F1.2 and DD increased significantly before 20 weeks gestation, while a statistically significant increase in FXIIa levels was first detected between weeks 20 and 30 of gestation. In pregnant women with aPS, increases in FXIIa were similar to those in normal pregnancy, but increasedFVIIa levels were not observed until after 30 weeks gestation.Similar to normal pregnancy, increased levels of TATandF1.2 were detected in aPS pregnancies before 20 weeks gestation, but increased DD were not observed until afterweek 20. Surprisingly, women with aPS receiving low molecular weight heparin prophylaxis had significantly higher (P 0.02) levels of TAT (median 8.6; interquartile range (IQR) 6.5–20.8) between weeks 20 and 30 of gestation compared to the normal pregnant population (median 5.9; IQR 4.7–7.9), thus indicating increased thrombin generationin women with aPS in mid-pregnancy.