Comparing the cerebro-placental to umbilico-cerebral Doppler ratios for the prediction of adverse neonatal outcomes in pregnancies complicated by fetal growth restriction

Objective The cerebroplacental ratio (CPR) has shown utility as a surrogate marker for fetal growth restriction and can be used to stratify the risk for adverse perinatal outcomes in affected pregnancies. However, recent studies suggest that its inverse, the umbilico-cerebral ratio (UCR), may be a better predictor of such outcomes. The aim of this study was to compare the prognostic accuracy of CPR to that of UCR Doppler in predicting short-term adverse perinatal outcomes in growth-restricted fetuses.Methods We conducted a secondary analysis using data from a prospective study on women referred for fetal growth ultrasounds between 26 and 36 weeks of gestation and with an EFW < 10th percentile by Hadlock standard. The CPR and UCR were converted into Z-scores adjusted for gestational age at ultrasound. Abnormal CPR was defined as Z-score below the 10th percentile for the gestational age and abnormal UCR as Z-score above the 90th percentile. We calculated sensitivity and specificity of the two Doppler parameters for predicting composite adverse perinatal outcome (APO) defined as the presence of any one of the following: umbilical cord arterial pH <7.10, Apgars at 5 min <7, NICU admission,grade III/IV intraventricular hemorrhage (IVH), neonatal seizure and death. Logistic regression analysis was performed, ROC curves plotted and the area under the ROC curve (AUC) were compared between CPR and UCR.Results Over the study period, there were 197 women meeting inclusion criteria, of which 27 (13.7%) had a composite adverse neonatal outcome. The sensitivity using CPR Z-score for predicting the composite APO was higher thanwas similar to using UCR Z-score (39.3% compared with 37%) for a similar specificity (94.7 versus 94.1), respectively. However, the positive predictive value (PPV) was higher for CPR (55% vs UCR 50%) and the negative predictive values (NPV) were similar. For a fixed false positive rate of 10%, the detection rates for adverse neonatal outcomes were 40% using either CPR or UCR. The AUC for CPR and UCR were 0.70 and 0.68, respectively.Conclusion This study did not find any advantage in utilizing the UCR over the CPR.