Effect of prolonged uterine blood flow reduction on fetal growth in sheep

The purpose of the present investigation was to study the effect of 7 days of uterine blood flow reduction on fetal growth. Reduction in uterine blood flow was accomplished by external occlusion of the terminal aorta in 20 pregnant sheep. Linear growth was monitored daily by means of a crown-rump length measuring device. The deliveries of oxygen, glucose, and lactate to the fetus, as well as their uptakes by the fetus, were determined before and after 7 days of uterine blood flow reduction and correlated with rates of fetal growth. Identical studies were conducted in nine control animals. Uterine blood flow reduction resulted in a significant decrease in fetal oxygen delivery and fetal arterial oxygen content. Linear growth rate decreased by 38% in the occluded animals during hypoxemia. In addition, there was a 20% reduction in daily weight gain in occluded animals compared with controls. There were no differences in the uptakes of oxygen, glucose, and lactate by the fetus. Positive correlations were found between linear growth rate and fetal arterial oxygen content (r2 = 0.25, P = 0.0001) and between linear growth rate and fetal oxygen delivery (r2 = 0.21, P = 0.0006). The correlations between linear growth rate and fetal oxygenation provide strong evidence of the central role of oxygen in the regulation of fetal growth.