Changes in vascular resistance in the umbilical and middle cerebral arteries in the human intrauterine growth-retarded fetus, measured with pulsed Doppler ultrasound.

To assess how different cardiotocographic (CTG) findings are related to changes in vascular resistance, 256 normal and 37 growth retarded (IUGR) fetuses from 27 to 41 weeks of gestation were studied. Immediately following CTG monitoring, pulsed Doppler was used to identify flow velocity waveforms in both the middle cerebral artery (MCA) and the umbilical artery (UA), and from these the Resistance Indices (RIs) in both arteries (RIMCA and RIUA) were calculated. Of the 37 growth retarded fetuses, 25 had normal CTG findings. Although only 3 (12.0%) of these fetuses had low RIMCA, 12 (48.0%) had high RIUA, statistically different (P less than 0.01) from normal fetuses. In 11 of 12 (91.7%) growth retarded fetuses with an abnormal CTG, there were low RIMCA values, significantly more (P less than 0.01) than in those with a normal CTG. As for RIUA, all 12 IUGR fetuses with an abnormal CTG had high RIUA values (100%), a much higher proportion (P less than 0.01) than was found in the normal CTG group. These results mean that intrauterine fetal growth retardation per se is associated with a chronic increase in the RI value in the umbilical artery. By contrast, cerebral vascular resistance appears to decrease in compromised conditions, as indicated by abnormal CTG findings.