The Role of Fetal Renal Artery Doppler in Predicting Intrauterine Growth Restriction: A Case-Control Study

Fetal growth restriction (FGR) is a clinically significant condition linked to increased perinatal morbidity, stillbirth, and adverse long-term neurodevelopmental outcomes. Conventional Doppler assessment using the umbilical artery (UA) and middle cerebral artery (MCA) provides well-established markers of placental insufficiency and fetal cerebral adaptation. However, these parameters often identify fetal compromise only in relatively advanced stages of disease. Consequently, a significant number of high-risk pregnancies complicated by FGR may not be detected early when relying solely on UA/MCA Doppler assessments. Evaluation of the fetal renal artery using Doppler ultrasonography has been proposed as a potential early indicator of systemic hemodynamic adaptation to chronic fetal hypoxia. This study aimed to evaluate fetal renal artery Doppler indices in FGR and assess their utility as early markers of fetal compromise and risk stratification.

A prospective observational study was conducted at RL Jalappa Hospital, Tamaka, Kolar, on 60 singleton pregnancies diagnosed with FGR, compared with gestational age-matched appropriate-for-gestational-age (AGA) controls from September 2025 to December 2025. Doppler velocimetry of the fetal renal artery was performed to measure pulsatility index (PI), resistive index (RI), and systolic/diastolic (S/D) ratio. Simultaneous assessment of UA and MCA Doppler was performed. Statistical comparisons were made using Student's t-test or Mann-Whitney U test.

Renal artery PI, RI, and S/D ratios were significantly elevated in FGR fetuses compared with AGA controls (p < 0.001), indicating increased downstream resistance and reduced diastolic flow. Renal artery PI demonstrated good diagnostic performance in detecting FGR, with a sensitivity of 86.7%, a specificity of 83.3%, and an overall accuracy of 85% at the optimal cutoff value. These findings indicate that renal artery PI is a reliable parameter for identifying fetuses at risk of growth restriction. PI may substantially influence clinical decisions, such as increasing monitoring frequency or advancing delivery timing when thresholds for potential compromise are approached. Renal Doppler indices correlated with the severity of growth restriction and the presence of oligohydramnios, suggesting early systemic adaptation prior to overt UA or MCA abnormalities.

Fetal renal artery Doppler indices are sensitive markers of early hemodynamic compromise in FGR. Incorporating renal Doppler into standard surveillance protocols may serve as a complementary parameter for evaluating FGR; however, its role in early detection and clinical decision-making requires further validation. Renal Doppler assessment should be considered when UA Doppler results are normal, but FGR is still suspected.