Background: Fetal growth restriction (FGR) is a major contributor to perinatal morbidity and mortality, primarily resulting from placental insufficiency. Doppler velocimetry provides insight into fetal hemodynamic adaptation; however, the temporal progression of these changes and their role in determining optimal timing of delivery remain incompletely defined.

Objective: To evaluate the temporal changes in fetal Doppler indices and their role in determining the optimal timing of delivery in pregnancies complicated by FGR.

Methods: A prospective longitudinal analytical study was conducted in a tertiary care center over 24 months, including 180 singleton pregnancies with FGR (≥24 weeks). Serial Doppler assessments of the umbilical artery (UA), middle cerebral artery (MCA), cerebroplacental ratio (CPR), and ductus venosus (DV) were performed. The progression of Doppler abnormalities and time intervals between stages were analyzed. Time-to-delivery analysis, Cox regression, and ROC curve analysis were used to assess associations with delivery timing and adverse perinatal outcomes.

Results: Doppler abnormalities followed a sequential pattern, beginning with increased UA resistance, followed by cerebral redistribution, abnormal CPR, and eventual DV changes. The median time intervals between stages progressively shortened, indicating accelerated fetal deterioration. Time-to-delivery analysis demonstrated that DV abnormalities were associated with the shortest interval to delivery (log-rank p < 0.001), followed by CPR and UA abnormalities. DV abnormalities showed the strongest association with adverse perinatal outcomes (HR 5.6), while CPR demonstrated good predictive performance (AUC 0.86). Adverse outcomes occurred in 35.6% of cases, with high rates of preterm delivery and NICU admission.