Fitting growth curves to head and abdomen measurements of the fetus: a multicentric study.

Three different mathematical models were fitted to ultrasonic measurements of the biparietal diameter, head circumference, and abdomen circumference obtained from 1,426 healthy fetuses. The linear cubic function gives coefficients comparable with most previous studies, but it does not thoroughly explain fetal growth throughout pregnancy. Both the exponential-power function and the logistic-logarithmic function fit the raw data well and theoretically reflect the biological phenomena of human fetal growth. The characteristics of each model are discussed.