OBJECTIVE: To investigate associations between combined hormonal contraception and progestogen-only contraception and risks of venous thromboembolism by progestogen and carriership of genetic hemostatic variations.
METHODS: This was a case–control study in Sweden carried out between 2003 and 2009, which included 948 patients with venous thromboembolism and 902 individuals in a control group, all aged 18–54 years. Information was obtained by telephone interviews and DNA analyses of blood samples. Radiologic referrals were used for case ascertainment. For comparisons, odds ratios were estimated by unconditional logistic regression analysis adjusting for smoking, body mass index (BMI), and immobilization.
RESULTS: The odds ratio (OR) for current use of combined hormonal contraception was 5.3 (95% confidence interval [CI] 4.0–7.0). Desogestrel combinations had the highest OR (11.4, 95% CI 6.0–22.0). The OR for injection of medroxyprogesterone acetate was 2.2 (95% CI 1.3–4.0). In users of combined hormonal contraception with the factor V Leiden mutation, the OR was 20.6 (95% CI 8.9–58). In women who used progestogen-only contraception and carried the factor V Leiden mutation, the OR was 5.4 (95% CI 2.5–13).
CONCLUSION: Risks of venous thromboembolism in association with combined hormonal contraception vary by type of progestogen and independently of BMI and smoking. Thrombophilic genotypes such as factor V Leiden increase risks of venous thromboembolism in users of combined hormonal contraception. Except for injection of medroxyprogesterone acetate, progestin-only contraception seems to be the least thrombogenic hormonal contraception for women carrying genetic hemostatic variations.
LEVEL OF EVIDENCE: II