Many women in all stages of pregnancy can safely hike at moderate altitudes of 5,000 feet or less with little risk of complications. However, when hiking at higher elevations, pregnant women must take into consideration three factors: altitude, acclimatization and exertion. All three factors play a critical role in determining the safety of mother and baby.
There have been few studies on pregnant women and the affects of altitude on the woman and the fetus so there is no scientific consensus on what the highest altitude is for hiking while pregnant. However, wilderness medicine physician Dr. Paul Auerbach recommends pregnant women not hike any higher than 12,000 feet since blood-oxygen saturation is relatively well maintained up to an altitude of 10,000 to 12,000 feet. Once above 12,000 feet, blood-oxygen levels decline rapidly and will decrease the oxygen supply to the baby.
While it is not possible to predict how anyone, including a pregnant woman, will react to altitude, there are some general guidelines to follow to reduce discomfort and to lessen the chance of experiencing mountain sickness. The safest approach to hiking at altitude is to be acclimated to that elevation prior to undertaking the strenuous activity of hiking. Stay at your initial altitude with little to no activity for the first three days to allow your body to adapt to the lower oxygen and atmospheric pressure. Stay well hydrated. Once you begin your hike, walk slowly and ascend no more than 1,000 feet per day once you are above 10,000 feet.
While exercise is considered to beneficial to mother and child during pregnancy, it is wise to avoid heavy exertion during the hike. Walk at an easy, comfortable pace and stop to take frequent rests and to elevate your feet. If possible, only carry the minimal supplies, such as food, water and clothing, in a backpack in order to travel as light as possible.
Make sure you have a thorough check-up with your physician before hiking at altitude to confirm that your pregnancy is not at-risk. In addition, have an emergency plan in place should you require medical attention, especially if you are in a remote area. This plan should include emergency contact information and quick-access routes to the nearest medical facility.