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A retrospective study was conducted of thromboembolism by interviewing 175 married and unmarried women aged 15-44 discharged alive within 3 years from 43 hospitals in 5 U.S. cities. Thromboembolism included venous or arterial thrombosis with or without pulmonary embolism cerebral and coronary thrombosis and pulmonary embolism without a known source. 175 hospital controls were matched pairwise with cases on hospital residence time of hospitalization race age marital status parity and pay status. Both groups were free of obesity chronic conditions associated with thromboembolism and contraindications to pregnancy and were presumably fertile. 67 cases and 23 controls had used oral contraceptives until 1 month before entering hospital; 11 cases and controls had discontinued pills earlier. Duration of use did not affect risk. There were 57 case-control pairs in which only the case had used pills compared to 13 pairs in which only the control had used pills. The relative risk of thromboembolism for users was estimated to be 4.4 times that for nonusers. The risk was higher for sequential pill users. 25% of the cases were attributable to oral contraceptives.(Authors modified)
Sartwell et al. (Sat,) studied this question.