Risk factors for clinical manifestations in carriers of Factor V Leiden and prothrombin gene mutations.

Carriers of Factor V Leiden and prothrombin G20210A gene mutations have an increased risk of developing thromboembolic events and adverse outcomes of pregnancy. The objective of the present study was to identify risk factors which may predispose carriers of Factor V Leiden and/or prothrombin G20210A gene mutations to develop thromboembolic events and adverse outcomes of pregnancy. A retrospective case-control study of 217 carriers of Factor V Leiden and/or prothrombin G20210A gene mutations at two tertiary centers between January 2000 and December 2006. Symptomatic carriers (cases) were compared with asymptomatic carriers (controls) for the following risk factors: environmental, cardiovascular, family history of thrombosis, and presence of other thrombophilias. For female carriers, we included the use of female hormones, pregnancy, and the postpartum period. Of the 217 carriers, there were 155 (71%) cases and 62 (29%) controls. Of the 155 cases, 90 (58%) had venous thrombosis and 26 (17%) arterial thrombosis. Among the 123 symptomatic female carriers, 55 (45%) had recurrent pregnancy losses and nine (7%) other adverse outcomes of pregnancy. The postoperative state and the presence of antiphospholipid antibodies were risk factors for thromboembolic events and adverse outcomes of pregnancy in 10 (6%) and 22 (13%) cases, respectively. The presence of antiphospholipid antibodies in symptomatic carriers increased the risk of developing thromboembolic events 4.4-fold. The postoperative state and the presence of antiphospholipid antibodies were significant risk factors for thromboembolic events and adverse outcomes of pregnancy among Factor V Leiden and/or prothrombin G20210A gene mutation carriers. Testing for the presence of antiphospholipid antibodies may be warranted in Factor V Leiden and/or prothrombin G20210A gene mutation carriers who develop these adverse clinical manifestations.