Chronologic change in Doppler indices in the umbilical and middle cerebral arteries in the Japanese fetus: JSUM Standardization Committee for Fetal Measurements

Background: Doppler velocimetry in both the umbilical and intracranial arteries has been widely used for evaluating fetal circulation. Although many indices in the flow velocity waveforms in these vessels have been proposed, they have not yet been standardized using a large population of human Japanese fetuses. It is necessary to clarify the chronologic change in Doppler indices in the middle cerebral and umbilical arteries in human Japanese fetuses of advanced gestation. Materials and methods: In a total of 1,216 cases of pregnant women between 20 and 41 weeks of gestation, the resistance indexes in the umbilical (UmARI) and middle cerebral arteries (MCARI) and the pulsatility indexes in both arteries (UmAPI, MCAPI) were measured. For each index, values of weekly intervals and the regression curves at the 5th, 10th, 50th, 90th and 95th percentiles were constructed as the normograms. Results: UmARI and UmAPI showed a gradual decrease with advance in gestational age. MCARI and MCAPI were parabolic in nature with a peak at approximately 30 to 31 weeks of gestation. Conclusion: Placental vascular resistance was proven to decrease gradually with advancing gestation. Cerebral vascular resistance showed a transient increase followed by a gradual decrease to term. The constructed normograms can be utilized for evaluating fetoplacental and cerebral circulation.