The risk of venous thromboembolism in users of postcoital contraceptive pills.

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.