A method based on a follow-up of dynamic behavior of 113mIn tracer labeling the mother''s blood at the uteroplacental region was given. After localization of the placenta, 2 exponential curves of the dynamic behavior of the tracer, 1 placental and the other myometrial, were obtained. Measurement was made in the 3rd trimester of pregnancy in 30 women with pathological pregnancies and in 51 pregnant control subjects. The clinically sensitive criteria for distinguishing between pathological and control placentas were found to be the ratio between the specific blood flow in the placenta and that in the myometrium (.lambda.P/.lambda.M) and the slope (.alpha.) of the straight line passing through the points of this ratio. The value of .lambda.P/.lambda.M for pathological pregnancies was 5.4 .+-. 1.0 (SD) vs. 1.7 .+-. 0.6 in control pregnancies. The value of .alpha. for pathological cases was 6.3 compared with 1.5 for control subjects. These tests may be useful in diagnosis of pathological pregnancies with interference in uteroplacental circulation.