Estimated Fetal Weight Calculator 2025: Hadlock, INTERGROWTH, WHO Formulas
Estimated Fetal Weight (EFW) predicts baby size before birth. Our calculator supports 5 gold-standard formulas using ultrasound measurements: AC, FL, HC, BPD. Track SGA, LGA, macrosomia risk.
Hadlock Formulas
| Formula | Parameters | Accuracy |
|---|---|---|
| Hadlock 4 | HC, BPD, AC, FL | ±8–10% |
| Hadlock 3 | HC, AC, FL | ±10% |
| Hadlock 2 | AC, FL | ±12–15% |
EFW Formula (Hadlock 4)
log₁₀(EFW) = 1.3596 − 0.00386(AC×FL) + 0.0064(HC) + 0.00061(BPD×AC) + 0.0424(AC) + 0.174(FL)
INTERGROWTH-21st vs WHO
- INTERGROWTH: Global, prescriptive, 3rd–97th
- WHO: Descriptive, population-based
- Use INTERGROWTH for international standard
Percentile Interpretation
| Percentile | Classification | Action |
|---|---|---|
| <3rd | SGA | Doppler, NST |
| 3rd–10th | Small | Monitor |
| 10th–90th | AGA | Normal |
| 90th–97th | Large | GDM check |
| >97th | LGA | Delivery plan |
Step-by-Step Example
32 weeks: AC 280mm, FL 60mm, HC 290mm, BPD 80mm
- Hadlock 4: EFW = 1950g
- INTERGROWTH: 55th percentile
- Status: AGA
Macrosomia Risk
- EFW >4000g → C-section consideration
- >4500g → High shoulder dystocia risk
- GDM: 15–45% macrosomia
Serial EFW
- Every 2–3 weeks if concern
- EFW drop across percentiles → IUGR
- AC most sensitive
Limitations
- ±15% error common
- Obese moms: Underestimate
- Oligohydramnios: Overestimate
Integration with Tools
FAQs
Which formula is best? Hadlock 4 if all measurements available.
EFW at 36 weeks? ~2800g average.
Twins EFW? Use twin charts — 10–15% smaller.
Conclusion
Use our 2025 EFW Calculator with your latest scan. Combine with growth trends for best outcomes. Always consult MFM.
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