Transportation by air ambulance of pregnant mothers from peripheral hospitals to specialized institutions is becoming increasingly common. There are potential hazards to the fetus because of the altitude during flight, particularly in the presence of partially compromised placental function. Adult and fetal neurohumoral and metabolic responses to acute hypoxia tend to protect the fetus for a limited time period. These include maintenance of uterine blood flow, redistribution of blood flow to essential fetal organs, temporary decrease in fetal oxygen consumption, and dependence on anaerobic metabolism. These compensations are adequate for the normal fetus but may not protect the already compromised fetus from the deleterious effects of hypoxia.