Altitude Sickness


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is altitude sickness?

Altitude sickness is a set of symptoms, ranging from mild to life-threatening, developing as a result of a person being exposed to lower than normal pressures of atmospheric oxygen (O2), during and after ascent to high altitude (generally more than 2,500 m [8,202 ft]). This could happen if you are in inadequately pressurized aircraft, but usually is the result of climbing to mountain locations without giving your body adequate time to acclimate (to get used to) the higher altitude.

Altitude sickness is classified as acute if it develops quickly (within hours to days), due to a rapid ascent in altitude. The form that acute altitude sickness can take ranges in severity from a simple headache, to multiple symptoms (weakness/fatigue, dizziness/lightheadedness, insomnia, gastrointestinal symptoms), to severe, life-threatening conditions in the brain and lungs that well discuss later in this report. A very different class of altitude sickness is chronic altitude sickness, which can affect the blood, lungs, and brain of people who live at high altitude on a long-term basis.

How common is altitude sickness during pregnancy?

Acute mountain sickness strikes 25 85 percent of people who travel to high altitude, but the percentage depends greatly on the altitude of your starting location, and on the site of arrival. For travelers to Colorado ski locations, for instance, the rate of altitude sickness is 25 percent, but the rate jumps to 50 percent for those arriving at the Himalaya mountains, and to 85 percent for people flying directly to Mount Everest.

Pregnant women are not more susceptible to acute mountain sickness compared with women overall. However, young adults are more susceptible to the condition compared with people above the age of 50 years. Thus, a pregnant woman has a fairly high risk of developing altitude sickness, if she ascends quickly (over the course of hours to a day) to high altitude locations, such as a skiing facility. The typical scenario for this would be a woman during early pregnancy when there are no particular restrictions on activity or a woman who travels later in pregnancy, not to ski but to accompany others on a vacation.

How is altitude sickness diagnosed?

Altitude sickness is a clinical diagnosis, meaning that the diagnosis is made based on your history and findings on the physical examination, although doctors also may require some common tests such as a chest radiograph and analysis of a sputum sample to rule out other conditions that can look similar to effects of altitude. The clinical exam also may include whats called a mini-mental status test, for reasons that will become clear below.

The altitude sickness that is relevant to most pregnant women is acute altitude sickness related to traveling to high altitude rapidly, but to check a patient for chronic altitude sickness doctors will also order blood tests and more specialized tests of the lungs.

As noted earlier, there are different degrees of acute altitude sickness, the mildest form consisting of just a headache, while slightly worse cases of the condition also include other symptoms that doctors will use to diagnose you, such as gastrointestinal symptoms, insomnia, fatigue, and dizziness or lightheadedness. Based on whether you report each of these sets of symptoms as not present, mild, moderate, or severe, the doctor will assign a value based on a point system of 0 3. These values will be added together to compute whats called the Lake Louise score for severity of altitude sickness.

Particularly if you have a high Lake Louise score, you also will be tested for signs of two serious altitude complications that constitute the severe end of the spectrum of altitude illness. One such complication is called high altitude cerebral edema (HACE), for which you can be tested with the mini-metal status test. The doctor also may check the retinas of your eyes with a technique called ophthalmoscopy, which can help show what is happening in the blood vessels of the brain. HACE can be fatal, but generally, the main danger of HACE is that it can lead to a fatal accident during mountain climbing, hiking, or skiing, because the person loses their judgment, kind of like being drunk. HACE is thus a major danger for those who are climbing in relatively inaccessible locations, where the fastest way to descend to lower altitude is by walking down. These are not the types of locations where pregnant woman should be traveling anyway, because the risk of being far from medical facilities is just as bad as the risk of developing altitude sickness.

The other severe altitude complication for which you will be tested if your altitude sickness looks like it could be severe is called high altitude pulmonary edema (HAPE). This is diagnosed based on whether you experience breathing difficulty, cough, weakness, or chest tightness, and whether the doctor finds signs, such as wheezing or a type of sound called crackles in listening to your lungs, bluish skin (called cyanosis), rapid breathing, or rapid heart rate.

Does altitude sickness cause problems during pregnancy?

Apart from the prospect of severe complications, such as HAPE and HACE (both of which can lead to maternal death), it is possible that acute altitude sickness can increase your risk of having premature labor and delivery and pregnancy-related bleeding problems. At altitudes about 2,500 meters (about 8,200 feet), there also is increased risk of developing other pregnancy complications, such as high blood pressure, preeclampsia (high blood pressure with organ problems that may result in abnormal levels of protein in the urine), abruptio placentae (detachment of the placenta from the uterus), slowed growth of the developing baby, and death of the baby. Some evidence suggests that risk for these complications is elevated particularly if a pregnant woman is dehydrated, or engages in vigorous exercise before acclimatizing (getting used to) the increased altitude.

In the case of chronic altitude sickness, everybody, whether pregnant or not, has an increased risk of pulmonary hypertension, which can be fatal, and also strokes.

Does altitude sickness during pregnancy cause problems for the baby?

Acute altitude sickness can increase the risk of the baby being born prematurely, directly because of the altitude sickness, and also as a result of the complication of preeclampsia (high blood pressure with organ problems that may result in abnormal levels of protein in the urine). The babys life and well-being also are at risk from the possibility of abruptio placentae (detachment of the placenta from the uterus), and reduced blood flow to the uterus and placenta, especially at altitudes above 2,500 meters (8,200 feet).

What to consider about taking medications when you are pregnant:

  • The risks to yourself and your baby if you do not treat the altitude sickness
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat my altitude sickness during pregnancy?

The main drug given, both for prevention and treatment of acute altitude sickness, is acetazolamide. Another medication, a corticosteroid called dexamethasone, is given to treat HACE, but also may be given as a prevention dru
g in people who are considered to be at medium to high risk based on how high and quickly they intend to ascend. Drugs that can be given to treat HAPE, include nifedipine, a class of drugs called phosphodiesterase 5 (PED-5) -inhibitors (sildenafil, tadalafil), and another class of drugs called beta-2 agonists. Although there has been some concern that acetazolamide might present a risk for the developing baby, studies have not found much evidence supporting this concern. It is well-established that corticosteroid treatment is very safe in pregnancy, so there is little reason to avoid dexamethasone if needed to treat or prevent HACE. Confidence is fairly high that nifedipine, sildenafil, and especially tadalafil are relatively safe during pregnancy. PED-5 inhibitors are thought to be safe during pregnancy. Beta-2 agonists are constantly under study, but thus far are recommended in pregnant women who have a particular need for them, such as in the treatment of a life-threatening lung condition.

Who should NOT stop taking medication for altitude sickness during pregnancy?

If you need medication for altitude sickness, because you are unable to descend immediately to lower altitude, the risks of stopping the medication outweigh the risks of continuing.

What should I know about choosing a medication for my altitude sickness during pregnancy?

You may find Pregistrys expert reports about the individual medications to treat altitude sickness here. Additional information can also be found in the sources listed at the end of this report.

What should I know about taking a medication for my altitude sickness when I am breastfeeding?

Its generally considered fairly safe to nurse when taking acetazolamide or nifedipine. It is known that corticosteroids, such as dexamethasone, build up in breastmilk mostly during the first four hours after a dose is given. Consequently, some doctors will suggest that the patient wait four hours after receiving each dose, then pump out her milk and discard it, then wait for new milk to accumulate and nurse the infant from that new milk. Some options for what to do about that missed feeding include: pumping earlier in the day and saving the milk to feed in place of the discarded milk, feeding formula for that one meal a day, or simply using formula for all feedings. A lactation consultant can help you if you would like to keep breastfeeding. It is true that many studies suggest that there are benefits to breastfeeding both to the child and the mother, its also true that in most such studies it has been difficult to separate the true benefits of breastfeeding from various socioeconomic factors that also relate to whether women chose to breastfeed over formula.

What alternative therapies besides medications can I use to treat my altitude sickness during pregnancy?

The principal and most effective treatment for acute altitude sickness actually is not medication, but to descend to lower altitude. You can lower your chances of getting altitude sickness in the first place or prevent it entirely, by ascending gradually to higher altitudes. A very effective tactic, one that has been known to mountain climbers for many years but applies to casual tourists, is to ascend as slowly as possible to an altitude extreme by afternoon, and then descend partway back down to sleep at an altitude that is higher than the starting point, but lower than the highest point that was reached during the day. One other treatment is continuous positive pressure breathing (CPAP) in which you wear a special mask attached to a machine while you sleep.

What can I do for myself and my baby when I have altitude sickness during pregnancy?

Avoid dehydration by drinking plenty of fluids, and descend to a lower altitude. However, as you are consuming fluids, keep track of whether or not you are urinating, and how much you are urinating. If you are drinking fluids and not urinating, this is a sign that you may be developing HAPE, in which case you should descend to lower altitude as soon as possible.

Resources for altitude sickness in pregnancy:

For more information about altitude sickness during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or read the following articles:


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Last Updated: 24-02-2020
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

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