The Oxygen Tension in the Placental Bloods of Goats ‡

The data presented here on the oxygen tension in the maternal and fetal bloods entering and leaving the placenta of the goat were obtained as a part of a wider investigation of the oxygen supply to the fetal kid. As the first step in the program we estimated the rate at which blood reaches the uterus of the goat at selected stages in gestation and the arterio-venous oxygen difference across that organ to obtain data on the oxygen consumption of the uterus and its contents.1 Next we examined the characteristics of the oxygen dissociation curves of the fetal and maternal bloods of goats and the degree to which their respective affinities for oxygen were affected by changes in hydrogen ion concentration.' The results were related in two nomograms-one for fetal, the other for maternal blood-that permit the easy estimation of the oxygen tension in a blood sample when its percentage saturation with oxygen and its pH are known. These nomograms have been used to estimate the oxygen tensions in the bloods entering and leaving the maternal and fetal sides, respectively, of the placenta at different stages in gestation and in different circumstances. Finally, the results presented here served as the basis for the estimation of the transplacental oxygen gradient, i.e., the difference in the oxygen pressure in the maternal and fetal bloods entering and leaving the placenta.