Thrombophilic Disorders and the Risk of Thromboembolic Events in Women on Oral Contraceptives and Hormone Replacement Therapy.

Objective: To evaluate the frequency and distribution of thrombophilic conditions in women with thromboembolic events (TEE) while on oral contraceptives (OC) or hormone replacement therapy (HRT). To assess the contribution of the duration of hormone use and a positive family history for TEE in predicting thrombosis.

Methods: Retrospective analysis of all case records of women who developed a TEE while on OC or HRT and who were referred for hypercoagulable evaluation to the Thrombosis and Hemostasis Section at a teaching hospital from 1999–2002.

Results: 65 women who were taking OC or HRT and developed a TEE were identified with one or more hypercoagulable disorders. 23 women tested positive for two or more hypercoagulable disorders: 16 had Factor V Leiden 3 of them were homozygous and 13 heterozygous, 5 were heterozygous for the prothrombin gene g20210a polymorphism, 26 had positive antiphospholipid antibody tests, 10 had elevated homocysteine levels, 4 had protein C deficiency and 7 had protein S deficiency. There were 65 thromboembolic events: 16 pulmonary emboli, 17 cerebrovascular events, 11 intra-abdominal vascular thromboses, 13 extremity deep venous thrombosis (DVTs), 5 superficial thrombophlebitis, and 2 retinal vein thromboses. Of the 65 women, 37% of patients had a positive family history of thrombosis. 52% had additional risk factors for thrombosis including smoking or obesity. 51% had been taking OC or HRT for > 1 year.

Conclusions: In this population, thrombophilic conditions contribute in most cases to TEE in women on OC and HRT. Approximately 50% of TEE occurred in women on OC or HRT for > 1 year. The burden of thrombosis associated with hypercoagulability in women on OC and HRT has been underestimated in prior studies by including only DVT/PE. Family and personal history of thrombosis must be thoroughly explored before initiating or continuing OC or HRT and a positive history of thrombosis may warrant a hypercoagulable evaluation.