🩺What is Fetal Growth Restriction?
Estimated fetal weight (EFW) is calculated from fetal biometric parameters using validated regression formulas. The Hadlock formula using HC+AC+FL is the most accurate. Results are compared against population-based growth curves to determine percentile for gestational age. EFW <10th percentile suggests SGA/IUGR, while EFW >90th percentile suggests LGA/macrosomia.
📊Clinical Assessment & Risk Scoring
Healthcare professionals use these validated clinical calculators, diagnostic scales, and risk scoring systems to assess the severity, prognosis, or therapeutic dosing requirements for Fetal Growth Restriction:
Estimated Fetal Weight (EFW) — Hadlock & Shepard
The estimated fetal weight (EFW) calculator uses Hadlock and Shepard formulas based on fetal biometric measurements including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). EFW is essential for detecting fetal growth abnormalities such as SGA, IUGR, and LGA.
🧬Diagnostic Logic & Scoring Breakdown
The calculator prioritizes the Hadlock formula with HC+AC+FL (most accurate). If HC is unavailable, it uses Hadlock AC+FL. Other combinations are used as fallbacks. The result is compared against gestational age-specific percentiles.
📢Clinical Significance & Implications
Accurate EFW estimation is critical for detecting fetal growth abnormalities and guiding delivery planning. Fetal growth restriction (FGR/IUGR) affects 5-10% of pregnancies and is associated with increased perinatal morbidity and mortality. Macrosomia (LGA/EFW >4000g) complicates 8-10% of pregnancies and increases risk of shoulder dystocia, birth trauma, and cesarean delivery.
💡 Clinical Assessment Scenario Example
GA 32w: BPD 80mm, HC 290mm, AC 280mm, FL 62mm. Hadlock EFW = 1850g (45th percentile). Interpretation: Appropriate for gestational age.
⚠️Clinical Assessment Pitfalls
❌ Mistake: Using BPD alone for EFW estimation
✅ Correction: BPD alone has low accuracy for EFW. Always include HC, AC, and FL for the most accurate Hadlock estimation.
🚑When to Seek Medical Attention
This reference supports clinical assessment of Fetal Growth Restriction; it does not replace urgent evaluation. Seek prompt in-person medical care if symptoms are severe, rapidly worsening, or life-threatening, or if you are unsure about a diagnosis or treatment plan. Patients should always consult their physician before starting or changing any therapy.
❓Frequently Asked Questions
Q: Which EFW formula is most accurate?
The Hadlock formula using HC+AC+FL is the most accurate, with a 95% prediction interval of approximately ±15-18% of actual birth weight. The Shepard formula (BPD+AC) is slightly less accurate but useful when only BPD and AC are available. All formulas become less accurate at extremes of fetal weight and in the third trimester.
Q: What is the clinical significance of EFW <10th percentile?
EFW <10th percentile suggests SGA or possible IUGR. Once detected, detailed assessment includes: amniotic fluid volume, Doppler velocimetry (umbilical artery, middle cerebral artery), fetal anatomy survey, and serial growth scans. Management depends on the underlying cause, gestational age, and severity. IUGR increases risks of stillbirth, neonatal acidosis, and neurodevelopmental delay.
📚Evidence-Based References
Medically Reviewed By
Dr. Khaled Hassan
MD, FACC | Cardiology
Dr. Khaled is a cardiology consultant with experience in acute cardiac care.