In vitro perfusion of human placenta. V. Oxygen consumption.

02 consumption by human term placenta has been measured during perfusion in vitro, with a technique that permits perfusion of the intervillous space as well as the umbilical circulation. The rate at which 02 was consumed was directly related to the rate at which it was supplied, within the limits studied. Previous estimates of 02 consumption yielded figures approximating 3 ml. per minute per kilogram of placenta, but these estimates were attained under conditions of limited oxygen supply. When oxygen was delivered to the placenta at rates believed to be those achieved in vivo, oxygen consumption approximated 10 ml. per minute per kilogram. This rate of 02 consumption is similar to those obtained from studies of animal placentas in vivo and is more consistent with that of an active metabolic organ. If one were to accept estimates of 02 consumption by the human fetus in utero, the present studies indicate that approximately one fifth of maternal oxygen supplied to the conceptus is diverted to support placental metabolism.