Estimated Fetal Weight (EFW) Calculator
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.
About
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.
Formula
Hadlock (HC+AC+FL): Log10(EFW) = 1.326 + 0.01007(HC) + 0.0438(AC) + 0.158(FL) − 0.00326(AC×FL); Hadlock (AC+FL): Log10(EFW) = 1.304 + 0.05281(AC) + 0.1938(FL) − 0.004(AC×FL); Shepard (BPD+AC): Log10(EFW) = 0.625 − 0.0016(BPD×AC) + 0.059(AC) + 0.1(BPD)
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.
Score Interpretation
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.
EFW Result — 0+
Estimated fetal weight in grams with percentile for gestational age.
Management: Interpret based on percentile. <10th = SGA/IUGR evaluation. >90th = LGA/macrosomia evaluation.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| SGA/IUGR | <10th percentile | Evaluate for growth restriction |
| AGA (appropriate for GA) | 10th-90th percentile | Normal fetal growth |
| LGA/Macrosomia | >90th percentile | Increased risk of birth complications |
Dr. Khaled Hassan
Dr. Khaled is a cardiology consultant with experience in acute cardiac care.
View medical review board & editorial policy →Example Calculation
GA 32w: BPD 80mm, HC 290mm, AC 280mm, FL 62mm. Hadlock EFW = 1850g (45th percentile). Interpretation: Appropriate for gestational age.
Related Conditions
Common Mistakes
Using BPD alone for EFW estimation
BPD alone has low accuracy for EFW. Always include HC, AC, and FL for the most accurate Hadlock estimation.