Ask the Experts: Mountaineering: How can it impact OC risk?

As the number of women rises in mountain climbing expeditions, what are the potential risks for increased risk of blood clots at high altitude, particularly for those using combined oral contraceptives (OCs)?

Members of Contraceptive Technology Update’s editorial advisory board, and A Pocket Guide to Managing Contraception co-author Miriam Zieman, MD, tackled this challenging question, which was submitted by a reader whose patient was planning an ascent of North America’s highest mountain, 20,320-foot Mount McKinley in Alaska’s Denali National Park & Preserve.

David Archer, MD, professor of obstetrics and gynecology and director of the Clinical Research Center at the Norfolk-based Eastern Virginia Medical School: I would suggest abstinence or condoms, based on research indicating increased incidence of thrombosis at high altitudes.1,2 As a climber at that level, the patient may not need contraception. I would recommend discontinuation of OCs at three weeks before the climb.

Michael Rosenberg, MD, MPH, clinical professor of obstetrics and gynecology at the School of Medicine and adjunct professor of epidemiology at the School of Public Health, both at the Univer-sity of North Carolina at Chapel Hill, and president of Health Decisions, a Chapel Hill private research firm specializing in reproductive health: Venous thrombolytic events (VTEs) are quite rare, even in OC users. Although this remains in the possibilities category, I would advise the patient to be sure that she keeps well hydrated and not to worry about VTEs on the climb, assuming there is no family history or other factors to suggest any possibility of increased susceptibility. The clinician also might remind the patient that simply being active is a good way of reducing risk.

Susan Wysocki, RNC, NP, president and chief executive officer of the Washington, DC-based National Association of Nurse Practitioners in Women’s Health: It would not be unwise for the patient to get a full physical, not just a Pap smear, before she goes on her trip. She might want to consult a travel nurse or physician about going to high altitudes. These providers can offer specific advice on how to prepare for going into the clouds.

• Zieman, assistant professor at the Atlanta-based Emory University: Upon ascent to high altitude, the body experiences hypoxia and dehydration. The dehydration is due to diuresis (whereby the kidneys attempt to excrete bicarbonate to compensate for the respiratory alkalosis induced by hypoxia), increased fluid loss due to increased respiratory rate, and increased sweat in a low-humidity environment. As a response to these factors, there is a rise in hemaglobin production, later heightened by increased excretion of erythropoeitin released by hypoxic kidney cells. The higher levels of hemaglobin and hematocrit contribute to increased blood viscosity. Increased viscosity and coagulability heighten the risk of stroke and venous thromboembolism.

One must weigh the risks and benefits of contraceptive alternatives; it may partly depend on how fast the climb is, says Zieman, who served as medical officer for an 1988 exploration of a new route without oxygen up the eastern face of Mount Everest in Tibet. If it were a quick up-and-down, there probably would not be a problem. If one is going to acclimatize to allow the body to produce more red blood cells, there could be a problem. An estrogen-free method would be best, but one needs to consider bleeding changes involved with various methods, since irregular bleeding would not be desirable.


1. Anand AC, Jha SK, Saha A, et al. Thrombosis as a complication of extended stay at high altitude. Natl Med J India 2001; 14:379.

2. Segler CP. Prophylaxis of climbers for prevention of embolic accidents. Med Hypotheses 2001; 57:472-475.