Different Progestins: Combined Oral Contraceptives and Venous Thrombosis

Combined oral contraceptives (OCs) have evolved during the past several decades, in terms of both estrogen dose and progestin compound. Now, investigators have conducted a meta-analysis of 26 studies to provide an overview of OC formulation and risk for venous thrombosis (VT).

Women using combined OCs faced an estimated 1 in 1000 risk for VT each year, 3 to 4 times the very low risk for VT faced by women using no hormonal contraception. Combined pills containing levonorgestrel carried the lowest risk for VT, while pills containing gestodene, desogestrel, cyproterone acetate, and drospirenone all carried a 50% to 80% higher risk for VT than levonorgestrel pills. In addition, modern doses of ethinylestradiol (<50µg) were associated with lower risk for VT.

Comment: Although the relative risks presented in this study were not adjusted for duration of pill use, obesity, or tobacco use, they reinforce the low absolute risk for venous thrombosis with use of any oral contraceptive, and the idea that the best pill for a given patient is the one she wants to take. OCs lower women's risk for ovarian and endometrial cancer and have been associated with lower all-cause mortality compared with no contraceptive use, and pregnancy is associated with higher risk for VT than is OC use (the first 6 weeks postpartum are associated with VT risk 22- to 84-fold higher than in nonpregnant women [MMWR 2011; 60:878]). That said, those who want to minimize their risk for VT as well as unintended pregnancy are probably best served by intrauterine or subdermal contraception.