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Frequent readers of the I Spy Physiology blog will know that topics such as altitude, pregnancy and exercise are some of our favorites to write about. All of these conditions provide a challenge to our body’s homeostasis, or ability of the body to regulate all of its systems and functions. Until recently, scientists did not know much about how the body responds to being pregnant at high altitude while engaging in a lot of physical activity at the same time.

A case study in the Journal of Applied Physiology on a pregnant native highlander who worked as a guide on the trek up Mount Everest recently made news because her situation challenged ideas about exercise during pregnancy. The woman was born and spent most of her life at or above high altitude (about 11,300 feet). By comparison, the highest city in the U.S. is Leadville, Colo., at about 10,200 feet above sea level. The woman was 28 years old and 31 weeks pregnant with her first child at the time of the high-altitude trek.

To try to understand what happens when altitude, pregnancy and exercise are combined, the researchers monitored the woman’s vital signs, including:

• heart rate,
• blood pressure,
• sleep patterns, and
• the number of red blood cells she had and the amount of oxygen they carried throughout her body.

The research team also noted the woman’s physical activity levels and whether she had any symptoms of acute mountain sickness. They found that the woman’s daily physical activity (roughly 270 minutes/day) was nearly twice the weekly amount of exercise recommended during pregnancy (about 150 minutes/week). Her sleep patterns, though interrupted, appeared to be normal for someone in the third trimester of pregnancy. The rest of the measurements changed as predicted in response to altitude, and she did not experience any symptoms of altitude-related illness. In other words, pregnancy did not slow her down much! After the trek, the woman delivered a healthy baby at 42 weeks. Ten months later when the researchers followed up, she was still doing well and guiding treks.

It’s likely that one of the reasons she was able to perform such high levels of activity without complication was because she is a highland native. Over time, people who live at high altitudes for long periods of time adapt to the conditions and physical challenges they present, such as breathing air that has less oxygen.

Despite the fact that approximately 200 million people live above 8,200 feet around the world, we generally know very little about the physical activity patterns and pregnancy outcomes in populations at high altitude. To better understand how people adapt to these environments, more work will have to be done.

Anne R. Crecelius, PhD, is an assistant professor in the department of health and sport science at the University of Dayton in Dayton, OH.