DEVELOPMENT OF ORGAN BLOOD FLOWS IN THE FETAL AND NEONATAL BABOON

Subhuman primates are frequently used as models of human perinatal physiology and pathology. In order to obtain normal data for organ growth and blood flow 65 measurements were made on baboons from 115 days gestation (term 184 days) to age 8 weeks during acute surgical experiments using the radioactive microsphere method to estimate cardiac output and organ blood flow.From 115 days to term, while body weight triples, biventricular cardiac output per kg body weight increases by about 50% -- a level that is maintained postnatally from birth to 8 weeks while body weight increases about 50%. Brain weight increases by about 150% during the last third of pregnancy while blood flow increases almost 6-fold. There is a significant decrease in cerebral blood flow in the transition from fetus to neonate but increased blood oxygen content maintains oxygen delivery at the prepartum level. Postnatally there is a 25% increase in brain weight and a comparable increase in blood flow with all of the increase in blood flow distributed to the cerebral cortex. In contrast, renal growth and blood flow over the age-span studied parallel changes in total body growth accounting for about 0.6% of body weight and about 4% of biventricular cardiac output.