Modeling gestational age centiles for fetal umbilicocerebral ratio by quantile regression analysis: a secondary analysis of a prospective cross-sectional study

Objective: There is a lack of evidence on whether to favor cerebroplacental ratio (CPR) or umbilicocerebral ratio (UCR) when assessing pregnancies at risk of fetal growth restriction. The Recent evidences highlight a significant heterogeneity in the methodology of previously published studies reporting reference ranges for Doppler indices, which may affect the clinical applicability of these charts. The aim of this study was to develop charts of UCR based upon a recently proposed standardized methodology and using quantile regression. Methods: This was a secondary analysis of a prospective cross-sectional study including low-risk singleton pregnancies between 24 and 40 weeks of gestation undergoing Doppler recordings. The UCR centile values were established by quantile regression at different gestational age intervals. Quantile regression analysis was used to build the UCR chart. Result: 2516 low- risk singleton pregnancies were included in the analysis. UCR decreased with advancing gestational age. The 3rd, 5th 10th, 50th, 90th, 95th, and 97th centiles according to gestational age are provided, as well as equations to allow calculation of any other percentile. Conclusions: We have established gestational age-specific normative centiles reference limits for UCR.