Letters Hormonal contraception and thrombosis

Any review must carefully weigh the available evidence

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f2250 (Published 16 April 2013) Cite this as: BMJ 2013;346:f2250
  1. Dustin J Costescu, contraceptive advice research and education fellow1,
  2. Ashley Waddington, contraceptive advice research and education fellow1
  1. 1Department of Obstetrics and Gynaecology, Queen’s University, Kingston, ON, Canada K7L 2V7
  1. dustin.costescu{at}queensu.ca

Helmerhorst and Rosendaal’s recommendation that women prescribed oral contraceptives should receive levonorgestrel and 30 µg of ethinylestradiol is based on the observation that thrombosis risk is related to ethinylestradiol amount and progestogen type.1 Although interesting, this strategy is not adequately evidence based.

Retrospective database studies of contraception and thrombosis are often cited because they are inexpensive and can rapidly amass large datasets. Unfortunately, conclusions are weakened by crucial methodological flaws, including lack of validation of diagnosis, lack of controls for confounders (including indication), and violations of time order.2 3 Furthermore, in the MEGA study, a case-control study cited by the authors, the confidence intervals of odds ratios for deep vein thrombosis and pulmonary embolism for cyproterone acetate and levonorgestrel overlap.4

Conclusions regarding progestogen type and thrombosis risk must be based on high quality prospective data that use appropriate comparators and active surveillance. Studies meeting these criteria have consistently failed to demonstrate differences in risk of venous thromboembolism between levonorgestrel and other progestogens. Recently, the Society of Obstetricians and Gynaecologists of Canada affirmed the comparable safety of third generation, fourth generation, and cyproterone acetate/ethinylestradiol formulations.5

Finally, we discourage a “one pill fits all” approach to contraception. Women benefit from a range of options that allow for a balance between indication, benefit, and risk. A restrictive prescribing practice is paternalistic and would probably increase dissatisfaction and non-adherence. The consequences of unintended pregnancy and contraceptive failure are serious and should not be underestimated.

We hope the European Medicines Agency will carefully evaluate the existing data and, in doing so, reassure women that oral contraceptives are safe (not risk-free). Meanwhile, we must continue to provide patients with a range of tools to prevent pregnancy and knowledge to assist in safe contraceptive decision making.


Cite this as: BMJ 2013;346:f2250


  • Competing interests: DJC has received honorariums from Pfizer (Canada) and Bayer Healthcare (Canada). AW has received honorariums from Bayer Healthcare (Canada), Merck (Canada), Pfizer (Canada), and Warner-Chilcott (Canada).

  • Full response at www.bmj.com/content/346/bmj.f1464/rr/638159