The Relationship Between Umbilical Artery Flow Parameters and Renal Artery Doppler Indices in Fetuses With Growth Restriction

Objectives To evaluate the relationship between umbilical and renal artery Doppler indices in fetuses with growth restriction (FGR) and to examine their association with amniotic fluid index (AFI), early‐ and late‐onset subtypes, and perinatal outcomes. Methods This prospective observational study included 151 singleton FGR pregnancies between 24 and 37 weeks of gestation. Doppler measurements of the umbilical, middle cerebral, ductus venosus, and renal arteries were performed by a single perinatologist. Fetuses were classified into four groups according to umbilical artery (UA) flow pattern: normal resistance, increased resistance, absent end‐diastolic flow (AEDF), and reversed end‐diastolic flow (REDF). Associations between Doppler indices, AFI, and neonatal outcomes were analyzed using Spearman correlation, while group comparisons were performed with the Kruskal–Wallis and Wilcoxon rank‐sum tests. Multivariable linear and logistic regression analyses were used to assess independent associations. Results Renal artery pulsatility and resistance indices did not differ significantly among UA flow groups, whereas a modest decline in the systolic/diastolic ratio was observed with increasing UA severity. Middle cerebral artery pulsatility index and cerebroplacental ratio decreased progressively, while ductus venosus pulsatility index increased across severity groups (all p < 0.001). Renal Doppler indices were significantly lower in early‐onset FGR but showed no independent association with NICU admission or neonatal death after adjustment. Conclusions Renal artery Doppler parameters provide complementary physiological insight into fetal hemodynamic adaptation in growth‐restricted pregnancies, particularly in early‐onset cases and those complicated by preeclampsia; however, their independent predictive value for neonatal outcomes appears limited.