Fetal and Placental O₂ Consumption and the Uptake of Different Metabolites in the Ruminant and Horse during Late Gestation

Abstract

The use of conscious pregnant animals with indwelling catheters in both fetal and maternal circulations has enabled a variety of measurements to be made on a long-term basis. In the sheep, changes in uterine and umbilical blood flows have been followed during the latter part of gestation (for references see Comline & Silver 1974) and such measurements coupled with analyses of arterio-venous differences in oxygen and other metabolites allow the calculation of fetal and utero-placental oxygen consumption and metabolite uptake (Battaglia & Meschia 1973). The picture which has emerged is that the rates of both uterine and umbilical blood flow keep pace with the growth of the fetus so that its oxygen uptake per unit weight remains relatively constant. However, in their calculations of the energy balance of the sheep fetus Battaglia & Meschia (1973) noticed that the amount of oxygen used by the fetus was greater than could be explained by the uptake and metabolism of glucose, amino acids and other possible metabolic fuels; at least 20–25% of the total oxygen consumption remained unaccounted for.