• Distinguishing pathological Fetal Growth Restriction (FGR) from constitutionally small-for-gestational-age (SGA) fetuses
• Standardizing research definitions and clinical triaging for growth abnormalities globally

• AC or EFW < 3rd percentile
• Absent End-Diastolic Flow (AEDF) in Umbilical Artery (UA)
• AC or EFW < 10th percentile PLUS UA-PI > 95th percentile AND/OR MCA-PI < 5th percentile

• Isolated Criteria: AC or EFW < 3rd percentile
• Contributory (need ≥2): AC or EFW < 10th percentile
• Contributory (need ≥2): AC or EFW crossing percentiles by > 2 quartiles (>50 percentile drop) on growth chart
• Contributory (need ≥2): Cerebroplacental ratio (CPR) < 5th percentile OR UA-PI > 95th percentile

• CPR is MCA-PI divided by UA-PI.
• A low index (< 5th percentile) strongly implies "brain-sparing" hemodynamics (vasodilation of fetal brain). In late FGR, CPR is often the ONLY abnormal Doppler metric before decompensation.

• Fetus meets SGA but not FGR (e.g., normal Doppler, steady growth): Reassure, schedule 2-3 weekly growth scans.
• Fetus meets FGR Criteria: Initiate intensive surveillance. Non-Stress Tests (NST), Biophysical Profile (BPP), and Doppler indices (UA, MCA, ductus venosus) 1-2 times weekly depending on severity.
• Absent end-diastolic flow (AEDF): Highly concerning. Accelerate surveillance. Consider delivery between 33+0 to 34+0 weeks after corticosteroids for lung maturation.
• Reversed end-diastolic flow (REDF) or Ductus Venosus abnormal A-wave: Critical hypoxia. Highly imminent risk of fetal demise. Immediate delivery if viability parameters allow (frequently 30-32 weeks).

Prior to 2016, there were over 100 different clinical definitions of FGR/IUGR published in medical literature. The Gordijn/ISUOG Delphi process was the first successful attempt to unify global Fetal Medicine societies under a single, pathophysiologically-driven definition.