Fetal oxygen consumption, carbon dioxide production, and glucose uptake in a chronic sheep preparation

Metabolic studies were carried out in 22 sheep fetuses free of operative stress. The studies included measurements of umbilical blood flow (175 ± 8 ml/min/kg), fetal oxygen consumption (5.99 ± 0.15 ml/min/kg), carbon dioxide production (5.65 ± 0.17 ml/min/kg), glucose uptake (3.06 ± 0.28 mg/min/kg), respiratory quotient (0.94 ± 0.01), and glucose/oxygen quotient·(0.41 ± 0.03). The studies demonstrated that fetal glucose uptake could be correlated with the glucose concentration difference betsveen maternal arterial and fetal umbilical arterial blood, as well as with maternal arterial glucose concentration. Umbilical arterial glucose concentration was a function of maternal arterial concentration over the concentration range studied. The study demonstrates that the fetal respiratory quotient is significantly less than one. These data suggest that the accumulation of carbon in the fetus for growth represents approximately 40% of the carbon intake in the growing fetal lamb.