The following equation proposed by Vinzileos (1987) uses four parameters, which should offer greater accuracy over equations with only one or two parameters. Femur length has the advantage of accurately reflecting fetal growth patterns. The addition of thigh circumference is believed to improve the accuracy of the fetal weight measurement, and may be most useful in predicting fetal weight when growth abnormalities are present.


estimated fetal weight in grams =

=10 ^ (1.897 + (0.057 * (biparietal diameter in cm)) + (0.015 * (abdominal circumference in cm)) + (0.054 * (femoral diaphysis length in cm)) + (0.011 * (thigh circumference in cm)))



• Abdominal circumference can be difficult to measure accurately by ultrasound.

• Biparietal diameter can be affected by variation in cranial shape.


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