Introduction. Because of their safety and efficacy, oral contraceptives are
available without prescription in many countries. Monophasic combined oral
contraceptives are a combination of estrogen and progestin taken in constant
amounts. Venous thromboembolism. Combined oral contraceptives slightly
increase the risk of venous thromboemolism, but this event is very rare among
non-pregnant women of reproductive age. The absolute risk rises with age,
obesity, recent surgery and certain forms of thrombophilia. The estrogen
component of combined oral contraceptives increases the synthesis of several
coagulation factors in a dose-dependent manner. Changes of most of these
parameters are very small and there is no evidence that they have any effect
upon the clinical risk of developing venous thrombosis. If a woman has an
inherited coagulation disorder that increases her risk of developing
thrombosis, the risk is increased several fold if she ingests estrogen
containing oral contraception. Conclusion. The increased risk of venous
thromboembolism associated with combined oral contraceptives should have
little impact on healthy women, but may have substantial impact on women with
a history of thromboembolism. Combined oral contraceptive use increases the
risk of venous thromboembolosm in a dose-dependent manner. The absolute risk
of venous thromboembolism rises with age, obesity, recent surgery and certain
forms of thrombophilia, as well.