Limitations:
Abdominal circumference can be difficult to measure accurately by ultrasound. Biparietal diameter can be affected by variation in cranial shape.
Hadlock (1984)
estimated fetal weight in grams =
= 10 ^ (1.5115 + (0.0436 * (abdominal circumference in cm)) + (0.1517 * (femoral diaphysis length in cm)) + (0.0006923 * (biparietal diameter in cm) * (head circumference in cm)) - (0.00321 * (abdominal circumference in cm) * (femoral diaphysis length in cm)))
Hadlock (1985)
estimated fetal weight in grams =
=10 ^ (1.3596 + (0.0064 * (head circumference in cm)) + (0.0424 * (abdominal circumference in cm)) + (0.174 * (femoral diaphysis length in cm)) + (0.00061 * (biparietal diameter in cm) * (abdominal circumference in cm)) - (0.00386 * (abdominal circumference in cm) * (femoral diaphysis length in cm)))
Roberts (1985)
estimated fetal weight in grams =
=10 ^ (1.6758 + (0.42478 * (biparietal diameter in cm)) + (0.01604 * (head circumference in cm)) + (0.01707 * (abdominal circumference in cm)) + (0.05216 * (femoral diaphysis length in cm)))
where:
• The above equation did not give valid answers; I suspect the biparietal diameter factor should be 0.042478.
• Valid for low birth weight fetuses.
