Most Progestin-Only Contraceptives Do Not Increase Venous Thromboembolism Risk

Compared with women who do not use hormonal contraception, women who take progestin-only contraception are not at increased risk for venous thromboembolism, according to the results of a new meta-analysis.¹ One exception to this finding, however, is women who use injectable progestins; there was some evidence that use of injectable progestins may be associated with an increased risk for thrombosis, but further evaluation is needed, said the study authors.

General consensus is that progestin-only contraception is the best choice for women at high risk for thrombosis despite that progestins have been shown to influence the risk of venous thromboembolism in combination estrogen-progestin oral contraception.^2,3 To evaluate whether progestin-only contraceptives is associated with risk of venous thromboembolism, the study authors analyzed 8 observational studies that met inclusion criteria. Study authors defined venous thromboembolism as deep venous thrombosis and pulmonary embolism.

In the 8 studies evaluated, 147 women had a venous thromboembolism. According to the study findings, the adjusted relative risk of a venous thromboembolic event ranged from 0.68 to 1.93 for users of progestin-only contraception versus nonusers of contraception, and no statistically significant difference was reported between study groups. A subgroup analysis to determine whether route of administration influenced the study results showed that the relative risk of venous thromboembolism was 2.67 for injectable progestin-only contraception versus nonusers of hormonal contraception.

The study authors point out that most women in the study used older progestins, such as levonorgestrel, lynestrenol, and norethisterone, which have been shown to carry less risk of venous thromboembolism than the newer progestins, including desogestrel, gestodene, and norgestimate.¹ These findings further support the recommendations that oral and intrauterine progestin-only contraception remain the best hormonal contraceptive choices for women considered at high risk for venous thromboembolism, such as women with hereditary thrombophilia, a history of estrogen-induced venous thromboembolic event, or a history of recurrent venous thromboembolism.^2,3

Pertinent Points:
- No association was found between use of oral progestin-only contraception and risk of venous thromboembolism in a meta-analysis evaluating 8 observational studies.
- Compared with women who do not use hormonal contraception, women who use injectable progestin-only contraception are twice as likely to have venous thromboembolism, but further analysis is needed to confirm this association.

References:

1. Mantha S, Karp R, Raghavan V, et al. Assessing the risk of venous thromboembolic events in women taking progestin-only contraception: a meta-analysis. BMJ. 2012;345:e4944 doi:10.11136/bmj.e4944.
2. Centers for Disease Control and Prevention. US medical eligibility criteria for contraceptive use. MMWR Early Release. 2010;59:1-86.
3. Department of Reproductive Health, World Health Organization. Medical Eligibility Criteria for Contraceptive Use. 4th ed. Geneva: WHO Press; 2009.