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Women’s high-altitude health: FAQ Expanded version.

After over three years of hard work by members of the UIAA Medcom they have completed a project looking at the medical evidence regarding women at altitude and earlier this month the work was presented at the WIlderness Medical Society/International Society of Mountain Medicine congress held at Snowbird in Utah USA.

The work includes detailed review of international literature on the subject published in the respected medical journal High Altitude Medicine and Biology. The main conclusion was that there is little detailed and reliable data on the subject but they have, with this in mind, a series of Frequently Asked Questions outlined below with references, answering a laypersons questions in plain English on this important subject. You can also find this on the UIAA website.

The following apply to:

• women travelling to high altitude (above 2500 metres)
  

• for physical recreation, including climbing, mountaineering, trekking for up to 3 months
  

Answers are based on the latest science and practical medical experience of the UIAA Medical Commission. We refer to sex (female or male) not gender as we focus on anatomical and physiological differences. Scientific references are listed at the base of the page.

1. Why is a pre-trip medical appointment a good idea for women?

Travel to unaccustomed altitude is a physiological challenge to any mountaineer. Three months prior to departure for higher climbs and longer trips we recommend a personal consultation with a doctor or nurse experienced in mountain and travel medicine. This will allow you to review your health and medical history, with adequate time for any required changes to regular medication to be monitored, immunisations to be administered, and nutritional deficiencies to be addressed.

At this appointment:

• Regularly taken medication should be reviewed for suitability: for use at altitude, and for potential drug interactions with altitude-specific medications including those that may be needed in an emergency to facilitate descent.
  
  
• Depending on the destination / intended altitude / planned speed of ascent your practitioner may also recommend travel medications(e.g. antimalarials) and drugs which may be helpful or needed at higher altitudes (e.g. altitude sickness prophylaxis).
  
  
• Hormonal contraception if used should be reviewed for the most suitable preparation for you and your trip type (duration, altitude), including options for period control if desired. A medical appointment 6 months prior to departure is recommended if you are considering starting injectable hormonal contraception or a hormonal intrauterine system, to allow time for monitoring to ensure it’s suitable for you.
  
  
• Check iron levels. Menstrual blood loss can deplete your body’s iron stores and lead to anaemia. Anaemia reduces your blood’s ability to carry the optimum amount of oxygen which will make high altitude climbing more difficult. If identified early a 3-month course of oral iron tablets can normally replenish your iron stores.

2. Periods at high altitude – what do I need to know?

There is no medical risk inherent with normal periods at high altitude, but long days of climbing and few washing / toilet facilities can make managing periods in remote areas more difficult. Also, travel to high altitude and the stress of travel may influence period timing and the amount of bleeding, so some women may prefer to control or suppress periods for convenience.

Periods can be controlled short-term (e.g. 3 months) by hormonal contraception. This can take several different forms. Combined pills are one of the most common forms, with period suppression being achieved by taking only the active (hormone-containing) pills. This means, according to the pill preparation, either taking the active pills as normal then omitting the pill-free week to skip directly to the next pack; or if your preparation contains placebo pills, taking the active pills then missing the 7 placebo pills to skip directly to the next active pills. There are also specific pill preparations for continuous period suppression.

Injectable hormonal contraception or intra uterine systems (e.g. hormonal coil) are often preferred by women who climb to high altitudes regularly, as these methods frequently either considerably reduce or stop all menstrual bleeding. With these methods there is no daily pill schedule to remember, and contraception effectiveness is not interrupted if you suffer a gastric upset.

Upsides of hormonal contraception period control

• Convenience and reassurance regarding pregnancy avoidance, knowing when your period will or won’t come.
  
  
• No known risks associated with delaying / suppressing your period for up to a year.

Downsides of hormonal contraception period control

• Having to remember to take a pill regularly can be difficult in remote locations and with time zone changes.
  
  
• A low but real thrombosis risk for certain pill formulas. Discuss this risk with your doctor if you are taking a contraceptive containing oestrogen.
  
  
• “Breakthrough” bleeding is possible in the first cycles of suppressing your period. Start several months ahead of travel to allow this to settle.

3. What do women need to know about contraception at high altitude?

Generally, the safest and most effective method of contraception at high altitude is the one you know and are already using. For many women this will be hormonal contraception, which contains various combinations of the hormones progestogen (progesterone) and oestrogen. Oestrogen can increase the risk of potentially dangerous clots forming in your veins, but studies about hormonal contraception at high altitude do not show any clinically relevant (notable) increase in blood clots in women who are healthy and active non-smokers. However, if you are going to very high altitude for a prolonged period it may be sensible to consider a contraceptive method without oestrogen. This can include a depot injection, an IUD (intrauterine device, also called a coil), or an IUS (intrauterine system, which is an IUD which secretes progestogen). These contraceptive methods may also simplify contraception because there is no daily pill schedule to remember, and contraception effectiveness is not interrupted in the case of a gastric upset, which is common in remote travel.

Some women may dream of conceiving a 6000m, 7000m, or even 8000m baby but it is normally best to delay such plans until you return to home altitudes. Travel through remote areas can expose you to infectious diseases which may not just make you ill, but require drug treatment, neither of which are ideal when pregnant. Whether mountaineering in a couple, or meeting someone new during travel, a reminder that unprotected sex exposes you to the risks of pregnancy and sexually transmitted diseases. Barrier contraception (condoms) and abstinence offer the only relative protection against sexually transmitted diseases.

More about contraceptives at altitude here.

4. AMS (Acute Mountain Sickness): Does it affect women differently from men?

Acute Mountain Sickness (AMS) is a non-fatal but potentially miserable condition that occurs when a person goes too high too quickly. AMS is normally experienced as a bad headache, with a range of other symptoms possible such as nausea, poor appetite, dizziness, sleep problems, and generally feeling poorly (malaise). It is rare for AMS to be experienced below 2500 metres.

Several studies have been published which look for sex differences in AMS but overall, no difference in the incidence of AMS for women and men has been established. Current evidence suggests that prevention and treatment should be the same for both sexes. Acclimatisation seems to be individual, with different people acclimatising at different rates. The best predictor of whether you are going to suffer from AMS is a history of previous AMS… which doesn’t help you much if you’re going to high altitude for the first time! Building experience over time and with increasing altitudes is your best protection.

Above 3000 metres we recommend an ascent rate of maximum 300 – 500m per day increase in sleeping altitude, with a rest day every 3 – 4 days (see video). Some doctors may prescribe prophylactic medications (e.g. acetazolamide) for those at particular risk. More about drugs at altitude here.

AMS may give you a crippling headache and it can progress to potentially fatal HACE (see Q5). Worsening symptoms may include completely losing your appetite, vomiting, extreme fatigue, and neurological symptoms such as decreasing coordination and consciousness (indicating HACE). AMS symptoms usually resolve within 2 days with rest at the same altitude; if symptoms do not improve within this time – or worsen – descent is vital.

Note: there are different ways of classifying and communicating AMS severity, including the Lake Louise Scoring system (LLS). LLS was created as a research tool and exists in several versions; when used as a diagnostic tool it can cause confusion. If communicating about a patient using LLS, specify the version you are using, and remember that the “clinical picture” (description of signs you see and symptoms the patient reports) is the clearest way to describe AMS severity. More here.

5. HACE, HAPE: Are there differences for women?

High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE) are potentially fatal high altitude illnesses. For HACE no overall sex difference has been established by science. For HAPE the incidence seems to be lower in women. There is currently no identified medical reason why women may be less susceptible to HAPE.

HACE or HAPE occur when the body’s attempt to compensate for lower oxygen availability at higher altitude (acclimatisation) begins to fail and leads to excess fluid accumulation in critical organs.

• In HACE, fluid builds in and around the brain. The resulting compression causes neurological signs: e.g. severe headache, poor coordination/balance, confusion, slurred speech and decreasing consciousness, leading to collapse, becoming unable to move even if necessary for survival. Death can follow rapidly due to respiratory depression (ineffective breathing).
  
  
• In HAPE, fluid builds in the lungs, causing breathing-related problems: a noticeable drop in exercise performance, increasing breathlessness even at rest, and cough often with pink, frothy sputum in the late stages. Everybody suffers a drop in performance with increasingly high altitudes, but a performance drop due to HAPE will be much more marked compared with the patient’s previous performance and other group members.
  
  
• Both HACE and HAPE can progress very quickly.
  

The best prevention is careful acclimatisation. Above 3000 metres we recommend an ascent rate of maximum 300 – 500m per day increase in sleeping altitude, with a rest day every 3 – 4 days (see video). Prescription of prophylactic drugs by an experienced mountain medicine physician may also be appropriate.

The definitive treatment for altitude illnesses is descent; for HACE and HAPE it is rapid, assisted descent with administration of appropriate emergency medication to buy time whilst descending. The absolute priority is for the sick person to descend without delay. Where possible it is best if they are carried rather than to descend under their own effort. Terrain and weather will dictate how this is achieved.

Learn more: HAPE case study

6. Is it safe for pregnant women to go mountaineering at high altitude?

It depends! Multiple individual factors are involved, and the science on this subject is limited. The few scientific studies available suggest that in a healthy nonsmoking pregnancy, brief or moderate duration exercise at altitudes up to 2500 metres add little extra risk to mother or foetus. However, our advice is conservative for this subject because we don’t know what we don’t know. It’s ethically and physically difficult to conduct research studies on pregnant women going mountaineering at high altitudes. Therefore, most of the knowledge we have on this subject is from studies on high altitude residents who do have a higher risk of pregnancy complications, and we don’t know what this means for low altitude residents visiting high altitude. When in doubt, consult your doctor.

Seek advice before you go.
If you know you are pregnant, seek medical advice prior to going to high altitude, ideally with an ultrasound to confirm the health of the pregnancy. Risk factors need to be assessed individually, according to your health, your history, and your travel plans. Anything you’re already suffering that is a risk factor to your pregnancy at home can be expected to be worsened when you add in hypoxia (reduced oxygen availability) due to altitude. A remote location can heighten the risk. The longer, later, and higher you plan to go, the more carefully preparation, exercise recommendations, and health checks must be made. If you go, ensure you have appropriate medical and rescue insurance.

Mountaineering at high altitude is difficult, even before you add pregnancy.
Remote travel, climbing exertion, coping with acclimatisation and AMS place demands on your body and mind. Add in a pregnancy, with the changes and extra demands it makes (cardiorespiratory changes, changing weight/balance, tiredness, etc) and you are adding another layer of complexity and hence potential risk to your adventure. For remote travel, it’s worth considering that infectious diseases such as diarrhea and malaria can be more severe in pregnancy, that some medications or vaccinations you may need may be contraindicated, and that you may be far from obstetric and medical care if you need it. Consider that joint laxity and changes to your centre of gravity and breathing can alter your sports ability and potential safety, especially after mid pregnancy. All that said, exercise is encouraged throughout pregnancy, and moderate mountaineering at moderate altitudes closer to home may be feasible for healthy and experienced mountaineers until well into pregnancy.

Exercise is good, overexertion is not.
It is generally recommended to avoid overexertion in pregnancy. One way to monitor this is to use the “talk test”; can you talk while doing the activity? You may be exercising too vigorously if you need to pause for breath after a few words. While exercise is certainly recommended in pregnancy, there is some evidence that babies of women who exercise frequently may have lower birth weights. We recommend not starting new mountain sports during pregnancy, and for those already participating, we recommend reducing the difficulty and intensity.

Acclimatisation must be respected.
Hypoxia affects you and potentially your foetus. If you do decide to go to high altitude, carefully complete acclimatisation prior to moderate exercise. Above 3000 metres we recommend an ascent rate of maximum 300 – 500m per day increase in sleeping altitude, with a rest day every 3 – 4 days (see video); pregnant women may require more rest. Heavy exercise above 3000 metres is best avoided. If you do go high and suffer from altitude sickness, prophylactic drugs, and treatments you might otherwise be prescribed may be unsuitable for you and the foetus. Be careful to maintain adequate hydration as the air at higher altitudes is drier, pregnancy + altitude + exercise cause hyperventilation, and the risks of dehydration in pregnancy are more complex.

Trimester matters.
The 1st trimester is when the foetal organs are formed and when early complications such as spontaneous miscarriage or ectopic pregnancy may occur, which can be life-threatening in a remote location. In 3rd trimester the main risks to consider are pre-term delivery and trauma. If you have a higher risk of any pregnancy complication (e.g. preeclampsia, multiple births, known miscarriage risk, etc) consult your doctor before going to high altitude, and when in doubt, avoid high altitude exposure.

Trauma – injuries that occur suddenly or unexpectedly such as falls and crashes – in pregnancy gets riskier as pregnancy progresses. Although the pregnant body prioritises protection of the foetus quite wonderfully (amniotic fluid to help absorb shock, thick uterine walls, pelvic bones), as the baby bump grows, it is more and more exposed, and even minor trauma can impact the pregnancy. Pregnant women instinctively try to protect their abdomens, which means that in a fall they may cause greater injury to themselves. If trauma does impact the abdomen, the force can injure the placenta or rupture the uterus, causing foetal death.

Update your harness
For pregnant women who want to climb we recommend adopting a full body climbing harness early in pregnancy. This type of harness wraps around your legs and shoulders with no weight-bearing webbing around your waist. It is both safer and more comfortable as the baby bump grows.

7. What nutritional considerations are important for women going to high altitude?

These include long-term nutrition prior to departure and at base camp and short-term food and fluid intake higher on the mountain. The available scientific data does not differentiate much between the sexes, therefore we offer the same advice to women and men except regarding iron status. Iron deficiency is more common in menstruating women and will affect your high-altitude health/performance, so have a blood test to assess your iron status 3 months prior to departure to allow time for a corrective course of supplementary iron if required.

Good nutrition is critical to maintaining performance when you are exerting yourself in the cold environment of high altitude. Adequate energy plays a critical role in high altitude safety including altitude adaptation, injury and illness prevention, and your ability to stay warm. The weight and bulk of food, fluid and fuel, and ease of preparation become increasingly relevant as you climb higher, coinciding with your energy expenditure and tiredness being at maximum. Adequate energy intake may be best achieved by choosing foods that appeal to you – and ideally that you’ve already verified are palatable to you at high altitude – rather than being too concerned about short-term nutritional balance.

High altitude induced anorexia (loss of appetite) may be partly caused by Acute Mountain Sickness (AMS). Prevention of AMS may therefore help you to better fuel yourself to ensure you can perform well at high altitude. Headaches attributed to AMS may be caused by dehydration, and vice versa. Ensure you drink adequate fluids to reduce your risk of dehydration, which is greater at higher altitudes and under exertion. If you have regular urine output (i.e. peeing) every 6 – 8 hours you are probably adequately hydrated.

If spending prolonged time at high altitude, weight loss can be a problem which also affects performance (especially given that some of the weight lost will be from muscle). Aim for generous quantities of food including carbohydrates, protein, and fluids when resting at base camp.

8. What is important for menopausal women on high altitude sojourns?

Menopause symptoms affect women individually. Some experience minimal symptoms, and for others symptoms are distressing and can affect well-being and exercise performance. If you are bothered by such symptoms, be prepared to handle them at high altitude with the same strategies you use at low altitude. If part of your strategy is Hormone Replacement Therapy (HRT) containing oestrogen, discuss this with your doctor prior to an extended high-altitude travel. Oral oestrogen may increase your risk of blood clots (thrombosis), whereas oestrogen via skin patches carries no increased risk. Science does not yet know whether short-term travel to high altitude affects menopause symptoms.

Whether taking HRT or not, there is no known extra risk of AMS for physically fit (post)menopausal women. The biggest AMS risk factor is a previous history of AMS, regardless of sex or age. Recommendations for AMS prevention (see Q4) are the same for menopausal women as for anyone else. Because age and menopause may alter your cardiopulmonary responses, and therefore acclimatisation and high-altitude performance, we recommend appropriate training in preparation for your high-altitude travel.

Other conditions to be aware of as you age and travel to high altitude are:

• Urinary Tract Infections (UTIs) are more likely after menopause and during remote travel with fewer hygiene facilities. Discuss with your doctor whether you should add preventative (e.g. vaginal oestrogen gels for post-menopausal women) or treatment (e.g. antibiotics) medications to your medical kit
  
  
• Both high altitude and age can increase sleep disordered breathing, which can cause sleepiness, decreased exercise performance, cognitive dysfunction and decision making. Proper acclimatisation is key to reducing this risk. Women with already identified Obstructive Sleep Apnoea should discuss management of their condition with their doctor before going to high altitude.
  
  
• Osteoporosis (bones weakening with age) is common after menopause. With osteoporosis your risk of fractures is higher, so continue any regular treatment while travelling, and exercise extra caution while moving through the mountains.

However, as weightbearing sports such as hiking are recommended to maintain bone mass and density – not to mention the mental health benefits of going to big nature – these risks should be weighed against the many benefits and pleasures of being in the mountains.

9. Are women at less risk of dying at high altitude?

There is some evidence from some areas that women may be less likely to die at high altitude than men. However, creating accurate statistics on mountain deaths is difficult. First, because there are thousands of mountains across the world and most people climb without registering themselves in a database or scientific study. Second, because many countries do not collate or share central statistics on fatalities. Nevertheless, there is some good data: for example the Himalayan registry holds quite complete long-term data, from which we learn that across all Himalayan peaks women are statistically less likely to die.

There is no obvious medical reason for a sex difference in mortality at high altitude. We can speculate that there might be behavioural, social, and cultural differences. Decision making may differ for women, for instance regarding team size, solo attempts, organisational logistics, or when to turn back. There is some evidence from the Himalayan region that women may be choosing to climb peaks where mortality is lower. The type of climbing adventure is also relevant, with notable differences irrespective of sex for groundbreaking technical exploratory mountaineering, commercial expeditions on established routes, or simpler trekking trips to altitude.

Regardless of sex, a sound mountaineering background gives more protection from harm than any other factor. Build your experience and proficiency over time, at different altitudes and in variable weather conditions, with expert teaching whenever possible.

10. About the UIAA women’s project – and where can I learn more?

This Q&A is based on a scientific research review project completed by the UIAA Medical Commission in 2024. Our goal was to summarise current knowledge about women’s health in short-term (up to 3 months), high altitude (above 2,500 metres) sojourns. After thorough research into the published English- and German-language medical literature our main finding was that little knowledge has been established because very little women-inclusive and sex-differentiated research has been published.

Even though women have travelled to altitude since the start of modern mountaineering and their numbers are increasing, the research so far has overwhelmingly studied men, with women in the minority or excluded. This is probably partly because setting up and conducting high altitude research is costly and difficult. Our literature search returned 7000+ potentially relevant articles, with most being excluded due to lack of relevance or duplication, leaving us around 500 studies to gather our knowledge from.

In summary, we learnt that:

• More women-specific and sex-differentiated research is required.
  
  
• There are very few identified sex differences that may predispose you to getting sick at high altitude. Therefore, our recommendations for the prevention and treatment of high-altitude illnesses are the same for both sexes.
  
  
• On some well-studied mountains there appears to be a lower death rate for women. There is not enough data available to know whether this is true across more mountains, or to explain why.
  
  
• Women appear to be less susceptible to High Altitude Pulmonary Edema (HAPE). There is no obvious medical reason yet identified.
  
  
• Women-specific issues (pregnancy, menopause) have for the most part not been studied in temporary visitors to high altitude. What we know mostly comes from studying populations resident at high altitude.
  
  

If this is of interest why not take a look at other posts on the blog? Or post a comment!
Better still, join the British Mountain Medicine Society! More information can be found here.

For more about the University of Central Lancashire's Diploma in Mountain Medicine (DiMM) take a look at this.

References

Each of the references below contains further detailed journal references.

Andjelkovic, Marija, et al. “Nutrition in Women at High Altitude: A Scoping Review—UIAA Medical Commission Recommendations.” High Altitude Medicine & Biology 25.1 (2024): 9-15.

Derstine, Mia, et al. “Acute Mountain Sickness and High Altitude Cerebral Edema in Women: A Scoping Review—UIAA Medical Commission Recommendations.” High Altitude Medicine & Biology 24.4 (2023): 259-267.

Horakova, Lenka et al. “Hormonal Contraception and Menstrual Cycle Control at High Altitude: A Scoping Review-UIAA Medical Commission Recommendations.” High altitude medicine & biology (2024): ## awaiting publishing detail

Horakova, Lenka, et al. “Women’s Health at High Altitude: An Introduction to a 7-Part Series by the International Climbing and Mountaineering Federation Medical Commission.” High Altitude Medicine & Biology 24.4 (2023): 243-246.

Jean, Dominique, and Lorna G. Moore. “Travel to high altitude during pregnancy: frequently asked questions and recommendations for clinicians.” High Altitude Medicine & Biology 13.2 (2012): 73-81.

Keyes, Linda E. “Hormonal contraceptives and travel to high altitude.” High Altitude Medicine & Biology 16.1 (2015): 7-10.

Kriemler, Susi, et al. “Frostbite and Mortality in Mountaineering Women: A Scoping Review—UIAA Medical Commission Recommendations.” High Altitude Medicine & Biology 24.4 (2023): 247-258.

Mateikaitė-Pipirienė, Kastė, et al. “Menopause and High Altitude: A Scoping Review—UIAA Medical Commission Recommendations.” High Altitude Medicine & Biology 25.1 (2024): 1-8.

Pichler Hefti, Jacqueline, et al. “High-Altitude Pulmonary Edema in Women: A Scoping Review—UIAA Medical Commission Recommendations.” High Altitude Medicine & Biology 24.4 (2023): 268-273.