An intravenous 133Xe method for measuring regional distribution of placental blood flow

A new method for measuring regional distribution of placental blood flow is presented. After 2-5 mCi of 133Xe saline has been injected intravenously, the counts over the placenta are registered with a scintillation camera interfaced with a digital data storage and television readout system. Using "area of interest" technique, time activity curves are obtained for different regions. Analysis of the curves is based on two-exponential curve fitting. In normal pregnancy the mean intervillous flow in 16 healthy women was 125 ml/min/100 ml and myometrial flow 17 ml/min/100 g. The intervillous flow in the central part of the placenta was 55% higher than in the marginal parts. The myometrial flow in the placental area was nearly the same as outside the placenta.