Shape changes during human fetal craniofacial growth.

An investigation into craniofacial growth during the fetal period was undertaken in order to measure changes in shape. Previous workers have reported little or no change in cephalometric angular measurements, leading to the conclusion that facial shape is stable, in contradiction to the changes in shape perceived by simple observation. The major problem has been the development of quantitative methods which accurately measure shape. The analytical method of morphanalysis was used in order to overcome the problem. Image outlines of fetuses were related to each other via a rectangular reference grid. The exact sites where growth changes occurred were plotted in relation to the coordinate reference grid and therefore could be isolated. The shape of the head was found to change progressively in all three dimensions during the fetal period. The impression given by cephalometric studies that facial shape is stable was not supported by the present investigation, which clearly demonstrated a progressive alteration in shape with age. It appeared that brain growth predominated over that of the face during the fetal period. This not only produced an alteration in the shape of the cranium, causing its elongation, but influenced the position of the nasomaxillary segment to which the musculature of the lower face in turn adjusted mandibular growth.