Estimation of the Doppler ultrasound umbilical maximal waveform envelope: II. Prediction of fetal distress.

Blood flow variables obtained via Doppler ultrasound (US) waveform estimation have been investigated for prediction of fetal distress. The umbilical flow was assessed using a number of waveform summary statistics in addition to the currently used resistance indices. We examined the relationship between umbilical artery waveform patterns and intrauterine growth restriction, preterm delivery and hypertensive disorders. To enhance prediction, we defined waveform skewness profiles based on pivotal points of the umbilical waveform that appeared to be related to the incidence of preterm delivery and that facilitated construction of IUGR prediction models. The data comprised 204 unselected pregnancies with the umbilical artery images recorded at 18 pregnancy weeks. The sample was divided into 114 pregnancies used to estimate model parameters and 90 pregnancies to validate the model. Logistic prediction models for detection of abnormal velocity waveforms associated with intrauterine growth restriction were derived, based on the waveform information. The estimated model sensitivity and specificity on the training data were 74% and 84%, respectively. Validation of the model on independent data yielded a sensitivity of 57% and specificity of 84%. The logistic IUGR prediction model appears to have significant predictive ability and potential for clinical use, even at this early gestational age. Our data suggest that prediction of IUGR at 18 pregnancy weeks can be much improved when the waveform shape is captured with a number of summary statistics in addition to resistance indices.