Postcoital contraceptive pills (PCP) have recently been approved for use as emergency contraception in the United States. The objective of this study was to assess the risk of idiopathic venous thromboembolism (VTE) in relation to exposure to PCP, and to better quantify the risk of idiopathic VTE associated with current oral contraceptive (OC) use and pregnancy. A population-based cohort study with a nested case-control analysis was conducted using women from the General Practice Research Database. There were no women with an outcome of idiopathic VTE with current exposure to PCP. The incidence rates for various exposures were 3.0/100,000 person-years for the unexposed, 5.3/100,000 person-years for second generation OC, 10.7/100,000 person-years for third generation OC, and 15.5/100,000 person-years in pregnant (or postpartum) women. The relative risk estimates were 1.7 (95% CI 0.3-10.5) for second generation OC, 4.4 (95% CI 1.0-18.7) for third generation OC, and 6.3 (95% CI 1.2-33.5) for pregnancy. Short-term use of PCP is not associated with a substantially increased risk for developing VTE.
PIP: A population-based cohort study with a nested case-control analysis was conducted to assess the risk of idiopathic venous thromboembolism (VTE) in relation to exposure to postcoital contraceptive pills (PCP) and to better quantify the risk of idiopathic VTE associated with current oral contraceptive (OC) use and pregnancy. The subjects were women less than 50 years of age who received PCP prescriptions at some time between January 1, 1989, and October 31, 1996. All subjects in the cohort of PCP users had a computer-recorded diagnosis from the General Practice Research Database. The results of the study indicate that there were no women currently exposed to PCP who had an outcome of idiopathic VTE. The incidence rates for various exposures were 3.0/100,000 person-years for those unexposed, 5.3/100,000 person-years for second-generation OCs, 10.7/100,000 person-years for third-generation OCs, and 15.5/100,000 person-years for pregnant (or postpartum) women. The relative risk estimates were 1.7 (95% CI, 0.3-10.5) for second-generation OCs and 4.4 (95% CI, 1.2-33.5) for pregnancy. Thus, the risk of VTE attributable to PCP is not substantially higher than it is for the risk for traditional OCs, despite the higher content of both estrogen and progesterone present in PCP.