Fetal Blood Volume and Fetal Placental Blood Flow in Lambs1

In the conscious, nonmedicated sheep fetus, blood volume strongly influences placental blood flow, a change of 1% in volume being associated with a change of 1.7 ± 0.1% in flow. This relationship is valid between blood volumes of 80 to 110% of normal, is independent of time over a period of several days and independent of concomitant changes in fetal hemoglobin concentration.We are indebted to Mr. Frederick Arfmann, Dr. J. Metcalfe and Mrs. Alice Fitzgerald for help with this study.