Is hiking at high altitude safe during pregnancy?

What does the evidence say about hiking at high altitude during pregnancy?

1. Exercise at or above 6,000 feet is listed among the activities to skip during pregnancy, alongside scuba diving and skydiving. 1
2. Federal altitude guidance calls it prudent for pregnant travelers not to sleep above 3,050 m, about 10,000 feet. 2
3. Acute mountain sickness affects about 25 percent of visitors sleeping above 2,450 m (8,000 ft) in Colorado, with headache as the cardinal symptom, usually starting 2 to 12 hours after arrival. 2
4. Pregnant travelers are advised to avoid activities at high elevation unless they have trained for and are accustomed to them, and to allow a slower ascent with time to acclimatize. 3
5. Comparing national guidelines, US guidance placed exercise up to about 6,000 feet (1,800 m) in the safe range, while Norwegian and UK guidance advise four to five days of acclimatization above 2,500 m and no hard exertion. 4

Is hiking at high altitude safe in each trimester?

• First trimester. Altitude sickness looks a lot like early pregnancy: headache, nausea, fatigue, no appetite. That overlap makes your own symptoms hard to read, so ascend slowly and keep the hiking easy.
• Second trimester. Many people feel strongest now and plan mountain trips. Build in acclimatization days, keep the pace conversational, and turn back if a headache does not settle with rest and fluids.
• Third trimester. Breathlessness is already common late in pregnancy and thin air adds to it. Remote trailheads also sit hours from obstetric care, which matters more as you get closer to your due date.