Measurement of intervillous and myometrial blood flow by an intravenous 133Xe method.

A new 'non-invasive' method for measuring intervillous and myometrial blood flow is presented. After 2 mCi of 133Xe in physiological saline was injected intravenously the patient held her breath for 20 seconds. The tracer entered the placenta as a short bolus and its removal was followed with a scintillation detector. Intervillous and myometrial blood flow per unit volume was calculated from the two-exponential curve. The mean +/-SD intervillous flow in normal pregnancy was 135+/-49 ml/minute/100 ml, the corresponding half time being 0-56+/-0-16 minutes. The myometrial flow was 7-7+/-2-5 ml/minute/100 g. The method gave reproducible results and took only 20 minutes to perform. The dose of radiation to the mother was less than 1 mrad.