Comparative value of growth velocity and umbilical artery Doppler for the prediction of adverse perinatal outcomes in growth‐restricted pregnancies

Abstract Introduction Fetal growth restriction (FGR) is associated with an increased risk of neonatal morbidity and mortality. Current diagnostic criteria for FGR do not discriminate between constitutionally small and pathologically restricted fetuses. Following FGR diagnosis, umbilical artery (UA) Doppler is utilized to monitor fetal well‐being, but its limitations have increased interest in investigating growth velocity as an adjunctive tool. The objective of this study is to compare the predictive ability of UA Doppler studies and growth velocity for adverse neonatal outcomes in growth‐restricted fetuses. Methods This is a secondary analysis of a cohort of pregnancies delivered in a single healthcare network from August 2017 to December 2022, diagnosed antenatally with FGR. The cohort was restricted to those with baseline estimated fetal weight (EFW) between the 3rd and 50th percentiles. All subjects had growth velocity measured (defined as EFW percentile change per week between baseline and subsequent ultrasound). The primary outcome was a composite of neonatal morbidity (neonatal intensive care unit [NICU] admission, low 5‐min Appearance, Pulse, Grimace, Activity, Respiration score [<7], intraventricular hemorrhage, necrotizing enterocolitis, or metabolic acidosis) and severe adverse perinatal events (stillbirth or neonatal death, hypoxic ischemic encephalopathy, mechanical ventilation, or severe metabolic acidosis [pH < 7.0]). Neonatal morbidity and severe adverse perinatal events were analyzed separately as secondary outcomes. Independence between growth velocity and S/D ratio was evaluated. Univariate logistic regression models were then performed, with each outcome of interest as the dependent variable and S/D ratio and growth velocity as independent variables. Receiver operating characteristic (ROC) curves were generated to compare the performance of both tests. Results A total of 172 patients were included in the analysis. UA Doppler data were available for 165 patients, 15.3% of whom had S/D ratio >95th percentile; none demonstrated absent or reversed end‐diastolic flow. There was no correlation observed between S/D ratio percentile and growth velocity, suggesting independence. ROC analysis demonstrated that the discriminatory ability of growth velocity was higher across outcomes with areas under the curve (AUC) ranging from 0.65 to 0.69 while AUC for S/D ratio percentiles ranged from 0.51 to 0.53, approximating the performance of chance. Higher growth velocity was significantly associated with reduced odds of the composite outcome (odds ratio [OR], 0.79; 95% confidence interval [CI], 0.69–0.90), and neonatal morbidity (OR, 0.84; 95% CI, 0.73–0.95). S/D ratio percentile was not associated with these outcomes. Conclusion In pregnancies complicated by growth restriction with forward UA flow, growth velocity outperformed S/D ratio percentile in predicting adverse outcomes. The two tests were independent, indicating that growth velocity may reflect a component of fetal development not captured by UA Doppler. These results suggest that growth velocity could be used in addition to UA Doppler studies for fetal risk assessment, especially in fetuses with forward arterial flow.