Risks of venous thromboembolism with various hormonal contraceptives.

Evidence There are no long-term RCTs, which leaves cohort and case-control studies as evidence. • The Society of Obstetricians and Gynaecologists of Canada1 and others2 have stated that evidence about the risk of VTE with different progestins is inconclusive owing to mixed results and a high risk of bias. • Some studies found no increased VTE risk with drospirenone3 or a transdermal patch.4 • Some studies found that different hormonal contraception did affect VTE risk: -Third-generation progestins (desogestrel, gestodene, drospirenone, or cyproterone) increased VTE risk (about 2 times) over second-generation progestins (like levonorgestrel or norethisterone).5-7 -Transdermal estrogen and vaginal rings increase VTE risk (about 2 times) over combined oral contraceptive pills (OCPs) with levonorgestrel.8 -Those using intrauterine devices with progestin or progestin-only pills have the same VTE risk as nonusers.7,9 -Lower-dose estrogen reduces VTE risk.1 • If these differences are real, the absolute risk of VTE per 10 000 woman-years (or 1000 women over 10 years) might be approximately -4 to 5 for nonusers, women using progestin-only pills, or progestin intrauterine devices1,7; -10 for users of OCPs with levonorgestrel or norethisterone1,7; and -20 (at most) for the transdermal patch or vaginal ring, and OCPs with desogestrel, gestodene, drospirenone, or cyproterone.7,8 -Absolute risk of pregnancy (for comparison) is 29.1