#70 What Is the Risk of VTE with Various Hormonal Contraceptives?
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- Studies that found different VTE risk between hormonal contraceptives:
- Combined oral contraceptives (COCs): 3rd generation progestins (desogestrel, drospirenone, gestodene, norgestimate, cyproterone) increase VTE risk (about 1.5-2x) over 1st or 2nd generation progestins (levonorgestrel or norethisterone).1-4
- Transdermal estrogen and vaginal ring increase VTE risk (about 2x) over combined oral contraceptive (COC) with levonorgestrel.5
- Levonorgestrel intra-uterine device (IUD) or progestin-only pills have same VTE risk as non-users.5
- Lower-dose estrogen reduces VTE risk.2
- Other studies found no increased VTE risk with drospirenone,6 transdermal patch,1 or vaginal ring.7
- If these differences are real, the absolute VTE risk per 10,000 woman-years (or 1,000 women over 10 years) may be approximately:
- 2-3 for non-users or women using progestin-only pills or progestin IUD.1
- 7-9 for use of COC with levonorgestrel or norethisterone.1-3
- 10-15 for use of COC with 3rd generation progestin, transdermal patch, or vaginal ring.1,3,5
- 29 for pregnancy (for comparison).1
- Society of Obstetricians and Gynecologists of Canada (SOGC)8 have previously stated evidence regarding risk of VTE with different progestins is inconclusive due to mixed results and high risk of bias.
- To keep the risk differences in perspective, 1,000-1,250 women would need to switch from higher- to lower-risk of COC to prevent one VTE per year.1,3
- Even the largest studies using confirmed VTE3-5 were retrospective and had potential confounding, leaving uncertainty if increased risk is real.
- Other factors influencing VTE risk are age (45-49 about 6x risk age 15-19),3,9 obesity (BMI ≥35 about 4x risk of BMI 20-25),3,10 and smoking (about 2x risk).3,10