Estimation of fetal weight from ultrasonic measurement of trunk circumference.

A new method of estimating fetal weight from the circumference of the fetal trunk, measured by ultrasound, is described. Comparison of weights estimated in this way with the actual birth weights of 50 fetuses, delivered not more than 48 hours later, shows a mean error in prediction of only 75 g, and in 94 per cent the error was less than 145 g. With such accuracy, the method is of clinical value, particularly in anticipating difficult delivery and in monitoring growth of the fetus at risk.