THROMBOTIC RISK-FACTORS AND ORAL CONTRACEPTION

Eighty-one women with a history of thrombosis were classified into thr ee groups: group I (n = 29), women in whom thrombosis developed during oral contraception; group II (n = 33), those who used oral contracept ives (OC) without complications but experienced vascular occlusion in other risk situations; group III (n = 19), women who never used OC. Th e level of antibodies to anionic phospholipids (PLa), a response to ac tivated protein C (APC), and the presence for the mutation in the coag ulation factor V gene causing APC resistance were studied. in the stud ied groups, APC resistance was present in 14% to 42% of patients, PLa were elevated in about half of APC-resistant patients, The incidence o f APC resistance correlated with the recurrency of the thrombotic even ts within the groups. In most cases it was tightly connected to the mu tation in the factor V gene. Women in whom thrombosis developed while they were taking OC (group I) differed from the others, having a remar kable disagreement between the lowest incidence of APC resistance and a relatively increased number of the mutation (14% vs 38%, p < 0.025). This finding suggested that the APC response is flexible. An influenc e of OC that predisposes a reduction in APC response is discussed.