Cerebral-umbilical Doppler ratio as a predictor of adverse perinatal outcome.

Using a 3.5-MHz duplex Doppler system, 45 normal-growth and 45 growth-retarded fetuses were studied between 30-41 weeks' gestation. Velocity recordings were obtained from the middle cerebral artery and umbilical artery to calculate the ratio between the two pulsatility indexes. The cerebral-umbilical Doppler ratio is usually constant during the last 10 weeks of gestation. Therefore, a single cutoff value (1.08) was used, above which velocimetry was considered normal and below which it was considered abnormal. The cerebral-umbilical Doppler ratio provided a better predictor of small for gestational age newborns and adverse perinatal outcome than either the middle cerebral artery or umbilical artery alone. In fact, in predicting those newborns who were small for gestational age, the cerebral-umbilical ratio had a 70% diagnostic accuracy [(true positive + true negative)/total number of cases], compared with 54.4% for the middle cerebral artery and 65.5% for the umbilical artery. The results were more encouraging for prediction of adverse perinatal outcome; diagnostic accuracy for the cerebral-umbilical ratio was 90%, compared with 78.8% for the middle cerebral artery and 83.3% for the umbilical artery.