Abstract

PIP: Ever since 1961, there has been discussion on possible thromboembolic effects from the use of oral contraceptives. The purpose of this Danish study was to determine if birth-control pill users did have an increased risk of venous thromboembolic disease (VTD), including deep venous thrombosis and pulmonary embolism. In previous research, morbidity from VTD has been found to show a great variance, as high as 1/330 woman years in 1 study to as low as 1/5,000 woman years in another. In these studies no significant difference was found between users and non-users of oral contraceptives. Only in 1 study was there found to be increased morbidity from VTD among pill users: 1/5,200 woman years, compared with 1/35,000 woman years for non-pill users. As a possible explanation of the pill's effect, several studies have demonstrated a rise in certain coagulation factors, increased fibrinogen and lowered antithrombin III. In the present study, medical records of all women aged 34 or under who had been referred to a Copenhagen hospital between 1981 and 1983 for treatment of phlebographic-or lungescintographic-confirmed VTD were investigated. After controlling for exclusion factors, there remained 35 test subjects between the ages of 16 and 34 (median age 22). Of the 22 cases of known etiology, 16 suffered from iatrogenic VTD. Of 13 women who suffered from VTD of unknown etiology, 69% were pill users, compared with only 29% (a significant difference) in a background-population interview study conducted in Denmark during 1983. With a known disposition to VTD, oral-contraceptive usage meant a relative risk of 0.9 for developing the disease, which figure conforms well with other cited research (in which the risk factor varied from 0.4 to 3.8).