Investigation of Deaths from Pulmonary, Coronary, and Cerebral Thrombosis and Embolism in Women of Child-bearing Age

Abstract

Inquiries were made by the medical field-officers of the Committee on Safety of Drugs about the use of oral contraceptives by 385 married women aged 20–44 who died during 1966 in England, Wales, and Northern Ireland from thrombosis or embolism of the pulmonary, cerebral, or coronary vessels. For comparison, information about the use of oral contraceptives was also obtained for a control series of women drawn from the same doctors' practices as those in which the fatalities occurred. A strong relation was found between the use of oral contraceptives and death from pulmonary embolism or cerebral thrombosis in the absence of predisposing conditions. The mortality from these two diseases attributable to the use of oral contraceptives by healthy women was estimated at 1.3 per 100,000 users aged 20–34 and 3.4 per 100,000 users aged 35–44 per annum. The women who died from coronary thrombosis in the absence of predisposing conditions had been using oral contraceptives more frequently than would have been expected from the experience of the control group, but the difference did not quite attain statistical significance, and the existence of a definite association is regarded as not proved. If it is considered justifiable to include deaths from coronary thrombosis in the above estimates of attributable mortality, they may be recalculated as 2.2 and 4.5 per 100,000 users per annum for women aged 20–34 and 35–44 respectively, figures which agree closely with the estimate of risk given by the Medical Research Council (1967) in its preliminary report. It is probable, however, that all these estimates of risk are too low because information from independent sources indicates that our control data substantially overestimated the use of oral contraceptives by the general population in 1966. No evidence was found that the risk of thromboembolism was associated with the use of any particular oral contraceptive formulation. Only 15% of the deaths of women who were found to have been using oral contraceptives were reported independently to the Committee on Safety of Drugs. © 1968, British Medical Journal Publishing Group. All rights reserved.