Siggelkow et al reported an equation for estimating the weight of a term fetus based on ultrasonographic measurements. The authors are from Johannes Gutenberg University, LMU (Munich) and University of Mainz.

Patient selection: term fetus


Mean time between the ultrasound exam and delivery was 7.2 days.


Parameters by ultrasonography:

(1) biparietal diameter in cm (BPD)

(2) thoracic diameter in cm (THD)

(3) femur length in cm (FL)


sum of the 3 parameters =

= SUM(measurement of the 3 parameters)


predicted birth weight in grams as published =

= (2.57 * (sum of the 3 parameters)) - 3,3330


predicted birth weight in grams as postulated=

= (2.57 * (sum of the 3 parameters)) + 3,3330



• The units for 2.57 is g per cm.

• The paper says that the constant is -3,330, but this gives results that are suspect.



• The mean absolute error was between 312 and 344 grams.

To read more or access our algorithms and calculators, please log in or register.