Fetal cerebral blood-flow redistribution: analysis of Doppler reference charts and association of different thresholds with adverse perinatal outcome.

In the gestational-age range of 32 to 36 weeks, adjustment of CPR or UCR for gestational age is not necessary when assessing the risk of adverse outcome in pregnancies at risk of fetal growth restriction. The adoption of absolute CPR or UCR thresholds, independent of reference charts, is feasible and makes clinical assessment simpler than if using percentiles or other gestational-age normalized units. The high variability in percentile threshold values among the commonly used UCR and CPR reference charts hinders reliable diagnosis and clinical management of late preterm fetal growth restriction. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.