• Baseline fetal weight estimation across the 2nd and 3rd trimesters
• Screening for Fetal Growth Restriction (FGR / SGA) via mapping to growth charts
• Assessing likelihood of macrosomia in diabetic pregnancies or post-dates

• Biparietal Diameter (BPD)
• Head Circumference (HC)
• Abdominal Circumference (AC)
• Femur Length (FL)

• Abdominal Circumference (AC) is the single most sensitive parameter for detecting altered fetal nutritional status (liver size/glycogen).
• Femur Length (FL) is generally the most preserved metric in asymmetrical growth restriction (brain-sparing effect).

• Hadlock algorithms inherently carry a ~10-15% margin of error on absolute weight. A 4000g estimate could realistically range from 3400g to 4600g.
• Severe oligohydramnios mechanically flattens the fetal abdomen, artificially shrinking AC and drastically underestimating EFW.
• Maternal obesity heavily degrades image quality and the reliability of caliper placement.

• Plot EFW on a validated local population curve (e.g., Williams, WHO, or INTERGROWTH-21st).
• If < 10th percentile: Assess for SGA/FGR. Initiate umbilical artery Dopplers and frequent fluid checks.
• If > 90th percentile: Suspect macrosomia/LGA. Optimize glycemic control, evaluate for shoulder dystocia risk, discuss mode of delivery if >4500g (or >4000g in diabetics).

Dr. Hadlock was a legendary diagnostic radiologist at Baylor College of Medicine. His relentless mathematical modeling in the 1980s formed the absolute bedrock of modern obstetrical ultrasound biometric screening.