Mathematical modeling of fetal growth: I. Basic principles.

Quantitative characterization of fetal growth requires the selection of measurement parameters and a growth curve model. For such studies we propose two new parameters (the head cube and the abdominal cube) and a new growth curve model [P = c(t)k+s(t)]. These parameters are relatively insensitive to shape changes and are related to three-dimensional parameters even though they can be calculated from profile diameter measurements. The growth curve model is capable of adequately describing a wide variety of growth curves and its coefficients may be associated with specific biological variables. The properties of these parameters and the growth curve model are discussed.