Umbilical blood flow, cardiac output, and organ blood flow in the immature baboon fetus

Seven immaturebbaboon fetuses were studied in an acute surgical protocol at 116 to 124 days' gestation (term = 184). Mean umbilical blood flow was 121 ± 29 ml. per minute per kilogram, mean cardiac output was 219 ± 30 ml. per minute per kilogram, and mean placental diffusion clearance of antipyrine was 75 ± 17 ml. per minute per kilogram. These data were similar to those previously obtained in mature baboon fetuses. Blood flow to organs drained by the superior vena cava was 50 per cent less in the immature compared to mature fetuses. Blood flow to the paleoencephalon as a percentage of cardiac output was significantly higher in the mature fetuses, a difference not completely explained by the increase in organ weight. One immature fetus was severely acidotic and showed the biochemical and circulatory changes associated with asphyxia.