The effects of a combination of cigarette smoking and oral contraception on coagulation and fibrinolysis in human females.

Oral contraception as well as cigarette smoking influence haemostasis. The simultaneous effect of both on blood coagulation and fibrinolysis was studied in nine female smokers. While continuing oral contraception after a 4-week abstinence from smoking the concentration of fibrinogen, antithrombin III and alpha 1-Antitrypsin decreased (P less than 0.01 or P less than 0.04) and of plasminogen increased (P less than 0.03). The other coagulation parameters remained unchanged. Although all determinations of these parameters were in the normal range, the observed trends were statistically significant. The concentrations of the fibrinopeptide A and B 15-42 did not differ. It is concluded that the observed alteration is caused by cessation from cigarette smoking.