Hypoxia

High altitudes produce stress on the human body such as hypoxia (reduced available oxygen), more intense solar radiation, cold, low humidity, wind (which amplifies cold stress), a reduced nutritional base, and rough terrain. Reproduction, in particular, at high altitudes affects increased infant mortality rates, miscarriage, low birth weights, and premature birth. An early study in Colorado reported that infant deaths are nearly twice as common above 8,200 feet (2,500 m) as at lower elevations. A common cause of fetal and material death is pre-eclampsia, a severe elevation of blood pressure in pregnant women after the twentieth gestational week.