Extended case-control study results on thromboembolic outcomes among transdermal contraceptive users.

BACKGROUND: We extended an earlier study that found a twofold higher risk of venous thromboembolism (VTE) associated with the transdermal contraceptive system relative to norgestimate-containing oral contraceptives (NGM-OC).

STUDY DESIGN: This case-control study identified potential cases of VTE, acute myocardial infarction (AMI) and stroke from 24 months of additional health care claims, with adjudication via medical records. Randomly selected controls were matched to cases on age (15-44 years) and characteristics of contraception use. Conditional logistic regression models provided odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS: The transdermal contraceptive system was associated with a twofold higher risk of VTE (OR 2.0; 95% CI 1.2-3.3) compared with users of NGM-OC. The OR for stroke was 0.6 (95% CI 0.1-3.2) and for AMI 1.2 (95% CI 0.3-4.7).

CONCLUSION: This extension was consistent with the earlier study, showing a twofold increased risk of VTE associated with use of the transdermal contraceptive system relative to NGM-OC.