Angular changes in cephalometric and centroid planes during foetal growth.

Alteration in shape of the cranio-facial region during the foetal period was measured by recording the angular changes between cephalometric planes and centroid planes. Cephalometric planes rely on locating anatomical landmarks whilst centroid planes join mathematically derived points. Centroid plane angles showed a higher correlation with age than cephalometric plane angles and were demonstrated to be a superior measure of change in shape. Both methods revealed a change in jaw relationship from Class III in the younger foetuses to Class II in the older ones. This was brought about by forward growth of the maxilla in excess of the much smaller forward movement of the mandible.