The oxygen tensión and acid-bases status of mother and fetus have been studied at delivery in 12 subjects from Lima (150 m.] and Cerro de Pasco (4,200 ,m.), Perú. Despite the low pO2 (60.7 ± 2 mm.Hg., x ± SEM) of maternal arterial blood at altitude, the tension of oxygen measured in microsamples of arterialized capillary blood from the fetal scalp was similar at altitude (19.0 ± 1.16 mm.Hg.) and sea level (21.5 ± 1.12 mm.Hg.). The fetus at altitude is born with a mixed acid-base disturbance that combines a respiratory alcalosis (pCO2 = 29.8 ± 3.4 mm.Hg.) with a metabolic acidosis (base-excess = -7.4 ± 1.6 m.Eq./L) and a pH similar to that found at sea level. The low fetal pCO2 correlotes welI with a decreased maternal pC02, at altitude, due to the additive effects of the hiperventilations of altitude and pregnancy (r = 0.77, p < 0 .001). There is a high degree of correlation betw...

The oxygen tensión and acid-bases status of mother and fetus have been studied at delivery in 12 subjects from Lima (150 m.] and Cerro de Pasco (4,200 ,m.), Perú. Despite the low pO2 (60.7 ± 2 mm.Hg., x ± SEM) of maternal arterial blood at altitude, the tension of oxygen measured in microsamples of arterialized capillary blood from the fetal scalp was similar at altitude (19.0 ± 1.16 mm.Hg.) and sea level (21.5 ± 1.12 mm.Hg.). The fetus at altitude is born with a mixed acid-base disturbance that combines a respiratory alcalosis (pCO2 = 29.8 ± 3.4 mm.Hg.) with a metabolic acidosis (base-excess = -7.4 ± 1.6 m.Eq./L) and a pH similar to that found at sea level. The low fetal pCO2 correlotes welI with a decreased maternal pC02, at altitude, due to the additive effects of the hiperventilations of altitude and pregnancy (r = 0.77, p < 0 .001). There is a high degree of correlation b...