DOPPLER EVALUATION OF CEREBRAL BLOOD FLOW IN THE DIFFERENTIAL DIAGNOSIS OF LATE-ONSET FETAL GROWTH RESTRICTION

Background: Late-onset fetal growth restriction (FGR) is associated with an increased risk of stillbirth and neonatal morbidity. However, the differentiation between FGR and small-for-gestational-age (SGA) fetuses in the third trimester remains challenging. Fetal Doppler assessment traditionally plays a key role and is considered to be a potential tool for risk stratification and optimization of obstetric management in cases of FGR. In recent years, there has been an active discussion about the role of cerebral blood flow in the targeted monitoring of fetal health and the improvement of perinatal outcomes. Objective: To study the diagnostic value of Doppler ultrasound parameters characteristic of centralization of fetal cerebral blood flow after 32 weeks gestation in the differential diagnosis of late-onset FGR and SGA, as well as their association with adverse perinatal outcomes. Materials and methods: This was a prospective study that included 140 pregnant women after 32 weeks gestation, namely 72 patients with SGA fetuses and 68 patients with late-onset FGR, selected according to the guidelines of the Russian Society of Obstetricians and Gynecologists (RSOG). All participants underwent Doppler ultrasound assessment; the cerebroplacental ratio (CPR) and umbilicocerebral ratio (UCR) were calculated. The findings of the Doppler study, performed as close to delivery as possible, were used for analysis. Changes in Doppler parameters in both groups were studied, and their correlation with perinatal outcomes was assessed using logistic regression analysis. Results: The comparison of perinatal outcomes showed that pregnant women with late-onset FGR compared to SGA fetuses had a higher rate of preterm birth, emergency delivery by cesarean section, birth of infants with a body weight below the 3rd percentile, and need for hospitalization of newborns in the neonatal intensive care unit (NICU). The parameters of Doppler ultrasound study (umbilical artery pulsatility index (UA PI), middle cerebral artery (MCA) PI, CPR, and UCR) in the late-onset FGR group more often exceeded the standard values. The median CPR was lower (1.19 vs. 1.70; p<0.001), and the median UCR was higher (0.84 vs. 0.59; p<0.001) in the late-onset FGR group compared to SGA. A significant association was found between UA PI, CPR, and UCR in pregnancies with FGR and adverse perinatal outcomes, such as preterm birth (OR: 76.3, p<0.001; 0.1, p<0.001; 26.5, p<0.001, respectively), emergency cesarean section due to fetal distress (OR: 4.1, p<0.05; 0.4, p=0.04; 4.5, p<0.05, respectively), neonatal hospitalization in the NICU (OR: 31.9, p<0.05; 0.1, p=0.04; 32.8, p<0.05, respectively), combined adverse perinatal outcome (OR: 13.3, p=0.002; 0.2, p=0.002; 11.2, p=0.05, respectively); however, ROC analysis (AUC, 95% CI) of the models for predicting combined adverse perinatal outcome showed low prognostic value of these parameters. The best diagnostic accuracy was demonstrated by the gestational age-adjusted centile values of CPR and UCR [0.695 (0.604–0.777) and 0.675 (0.582-0.758)], as well as the dichotomized by a predetermined centile values of UCR <5th centile and PCR>95th centile [0.641 (0.547–0.727) and 0.631 (0.538–0.718)]. No data were obtained to support the greater effectiveness of CPR or UCR. At the same time, extreme values characterizing the centralization of cerebral blood flow became more obvious and clearer for interpretation in case of using UCR. Conclusion: Doppler parameters that characterize cerebral blood flow centralization, such as UA PI, MCA PI, CPR and UCR, are not effective enough to predict combined adverse perinatal outcome and its individual components in pregnancies with SGA fetuses and FGR. Gestational age-adjusted centile (continuous) values of CPR and UCR, as well as dichotomized by a pre-established cutoff centile value of CPR (<5th centile) and UCR (>95th centile) are more effective in predicting adverse perinatal outcomes. Further prospective studies are required to determine whether it is possible to include these parameters in clinical practice, as well as to find new markers that can predict adverse outcomes for children with late-onset FGR. © 2025 Elsevier B.V., All rights reserved.