Beyond biometry: the role of fetal venous doppler in discriminating fetal growth restriction from small for gestational age and predicting adverse perinatal outcomes

The distinction between fetal growth restriction (FGR) from small for gestational age (SGA) remains a major clinical challenge due to overlapping biometric features. The aim of this study was to evaluate the role of fetal arterial and venous Doppler parameters in distinguishing FGR from SGA and in predicting adverse perinatal outcomes. In this prospective case-control study conducted at a tertiary referral center, 120 singleton pregnancies between 32 and 39 weeks’ gestation were classified into FGR, SGA, and appropriate for gestational age (AGA) groups. Doppler examinations included the pulsatility index (PI) and the systolic/diastolic (S/D) ratio of the umbilical, middle cerebral and uterine arteries as well as the inferior vena cava, pulmonary and hepatic veins. Composite adverse perinatal outcomes (CAPOs) were also interpreted. The pulmonary vein (PV) PI and inferior vena cava (IVC) S/D were significantly higher in the FGR group than in the SGA group (p = 0.033 and p = 0.039, respectively). Cut-off values for FGR prediction were determined in the ROC analysis: PV PI > 1.7 and IVC S/D > 3.29. PV S/D and PV PI were also independently associated with CAPOs (p = 0.006 and p = 0.027, respectively). Univariate analysis confirmed PV S/D and PI as independent predictors of CAPOs. Fetal venous Doppler parameters, especially PV PI and IVC S/D, enhance the diagnostic discrimination between late onset FGR and SGA and may aid in the early prediction of neonatal complications. These findings suggest their potential role in improving fetal risk prediction beyond standard fetal biometry.