[Reaction of mother and fetus to physical stress at high altitude]

The objective of the study reported here was to investigate the reactions of mother and fetus to high-altitude hypoxia combined with physical exercise. The climb was passive, by means of scheduled journeys of the Grap Sogn Gion AG aerial cableway in Laax (Switzerland). The valley station is at an altitude of 1100 m, the mountain station at 2200 m. The mother exercised on a bicycle ergometer set to 25 watts for 3 minutes. The following were measured continuously and noninvasively: heart rate, respiratory rate, systolic and diastolic blood pressure, Po2 and Co2, uterus activity, and fetal heart rate. Twelve pregnant women with an average gestational age of 36 weeks (30th-39th week) took part in the study. Ten of the women were primiparae and two multiparae. During the trip up the mountain the barometric pressure dropped on average from 668 to 583 mmHg. This resulted in a maximum difference in Po2 between the valley and mountain stations of 18 mmHg. There were no systematic changes in Po2. Respiratory rate, heart rate, systolic and diastolic blood pressure remained unchanged during the trip up the mountain. The physical exercise at the mountain station led to an increase in respiratory rate from 12 to 20 min-1, while heart rate rose from 103 to 128 min-1, systolic blood pressure from 117 to 144 mmHg, and diastolic blood pressure from 70 to 90 mmHg. Six of the 12 women had regular contractions even during the trip up the mountain; these either remained unchanged or became less frequent in the course of the study. The mean fetal heart rate only changed slightly.(ABSTRACT TRUNCATED AT 250 WORDS)