How is fetal weight estimated?

Question

Accepted Answer

This site uses the Hadlock-4 formula published by Dr. Hadlock in 1985. It estimates fetal weight (EFW) from four ultrasound measurements — biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) — and is the standard formula in OB-GYN practice. Expect ±10–15% error vs actual birth weight, with larger error in late pregnancy and at extremes (macrosomia, low birth weight) where other formulas may fit better. Use all four values from the same scan date. If your hospital's estimate differs, defer to the hospital.