Predictive ability of cerebroplacental ratio for adverse perinatal outcome in the third trimester

Introduction and aims: Fetal growth restriction is associated with increased risk of adverse perinatal outcome. The aim was to investigate the potential of cerebroplacental ratio (CPR) to predict adverse perinatal outcome in high-risk pregnancies in the third trimester. Another aim was to study if CPR has better predictive value than its components, middle cerebral artery (MCA) pulsatility index (PI) and umbilical artery (UA) PI. Methods: A register-based study including 1573 singleton high-risk pregnancies with Doppler examinations at 32+0 to 40+6 gestational weeks at two perinatal centers between 1994 and 2017. Receiver operating characteristics (ROC) curves were used to investigate the predictive value of the gestational age-specific z-scores for CPR, UA PI and MCA PI, respectively, for the outcome “perinatal asphyxia/mortality”, “birthweight small for gestational age (SGA)” and two composite outcomes: “non-SGA liveborn infants with neonatal morbidity” and “SGA liveborn infants with neonatal morbidity.” Sub-analyses were made for pregnancies with spontaneous onset of labor and trial of labor. Results: The performance in predicting perinatal asphyxia/mortality was poor for all three variables and did not differ significantly. The ROC area under curve (AUC) was 0.56, 0.55 and 0.53 for CPR, UA PI and MCA PI, respectively. CPR performed significantly better than its components in predicting SGA, ROC AUC 0.73. The ability of CPR and the MCA PI to predict the two composite outcomes were similar and significantly better than UA PI. In the sub-analyses the results were similar, but CPR performed significantly better in predicting “perinatal asphyxia/mortality” than its components, although the predicting ability was poor. Conclusions: All three Doppler measures were poor in predicting perinatal asphyxia and mortality. CPR and MCA PI were equally good in predicting neonatal morbidity, especially in SGA pregnancies, and both were significantly better than the UA PI. CPR had high predictive value for SGA at birth.