EFFECT OF FETAL METABOLIC ACIDOSIS UPON OXYGEN ENVIRONMENT

The occurrence of metabolic acidosis in the fetus is usually secondary to one occurring in the mother or is accompanied by fetal hypoxia. Pure fetal metabolic acidosis was produced in a series of lambs in utero at term by the infusion of hydrochloric acid. The uterine and umbilical blood flows were measured. By the simultaneous measurement of a variety of gaseous parameters in maternal and fetal blood, the oxygen consumption of the fetus was calculated. A consistent increase in umbilical vein oxygen tension was found, not explained on the basis of consistent alterations in uterine or umbilical blood flows. An umbilical vein and umbilical artery hydrostatic pressure increase was found, for which at present no explanation is at hand. It is suggested that the change in oxygen affinity of the fetal blood, produced by the Bohr effect, is the most likely explanation for the increase in oxygen tension found in the umbilical vein. © 1969.