Oral contraceptives and fatal pulmonary embolism

Abstract

In a national case-control study of fatal pulmonary embolism in New Zealand women of childbearing age, we estimated that current users of combined oral contraceptives had a relative risk of 9.6 (95% CI 3.1-29.1). From national distribution data, the absolute risk of death from pulmonary embolism in current users was estimated to be 10.5 per million woman-years.

PIP: This national case-control study examined relative risk of fatal pulmonary embolism in childbearing-aged New Zealand women who use combined oral contraceptives (OCs). A total of 36 cases were identified from deaths between January 1990 and August 1998. Information about medical and contraceptive histories from the group practice and any family planning clinic records, were obtained by the same approach for cases and controls. Overall, it was estimated that users of combined OCs had a relative risk of 9.6 (95% confidence interval, 3.1-29.1). However, from the national distribution data, the absolute risk of death from pulmonary embolism in users was estimated to be 10.5 (6.2-16.6) per million woman-years. This death rate was higher than expected, because the annual incidence of venous thromboembolism in OC users has been estimated at 1 or 2 per 10,000 women, with a case fatality rate of only 1-2%. Given these findings, the authors concluded that deaths from pulmonary embolism are rare among OC users, but the absolute risk should still be considered as clinically important and significant to public health.