Objectives: To investigate the screening performance and best threshold centile (5th vs. 10th) of the cerebroplacental ratio (CPR) in low-risk, term pregnancies to predict low birthweight and adverse intrapartum and neonatal outcomes in a term, low-risk population. Methods: This was a blinded, prospective, cross-sectional study of low-risk singleton pregnancies at term. Women attended fortnightly from 36 weeks for CPR and estimated fetal weight assessment. Intrapartum and neonatal outcomes were recorded. Primary outcomes assessed were low birthweight, cesarean section for intrapartum fetal compromise, and composite adverse neonatal outcome. Results: A total of 483 women participated in the study. The CPR 10th centile (1.48) threshold resulted in the best screening performance. Sensitivities for low birthweight, cesarean section for intrapartum fetal compromise, and composite adverse neonatal outcome of 41.9, 61.1, and 38.3% were achieved for false-positive rates of 17.7, 17.7, and 15.2%, respectively. The corresponding areas under the receiver operating characteristic curves were 0.62, 0.72, and 0.62. Conclusion: The CPR 10th centile resulted in the best screening performance, although this would be considered fair at best. The CPR 10th centile may be useful as part of a risk stratification tool for prediction of low birthweight and adverse intrapartum and neonatal outcomes.

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