QUANTITATIVE-EVALUATION OF CRANIOFACIAL GROWTH IN THE 3RD TRIMESTER HUMAN

A detailed understanding of fetal craniofacial growth is necessary for understanding the mechanisms underlying the growth process and how al tered growth patterns may give rise to specific craniofacial anomalies , Although descriptive studies of human fetal craniofacial growth are abundant, quantitative studies are less common; most employ only later al cephalograms or tracings of sectioned specimens, In this study, we compared growth rates in the individual bones of the facial and basicr anial regions in a large sample of spontaneously aborted, third trimes ter fetuses, Growth in the individual dimensions of most bones is not significantly different from isometry when compared with body weight, but comparisons of dimensions within bones show clear changes in shape , In particular, the mandible is characterized by a deepening of the c orpus, probably in association with development of the teeth, The maxi lla also shows a relatively rapid height increase associated with dent al development, The temporal bone grows faster in superoinferior heigh t as opposed to anteroposterior width, The lateral and inferior margin s of the zygomatic bone grow faster than the orbital margin, The basio ccipital bone, cited in radiographic studies as growing substantially slower than the facial region, actually changes in shape more rapidly than any other skeletal component examined in this study, with widths growing much faster than lengths, Our findings demonstrate that cranio facial development in the third trimester is characterized by localize d variation in the rate of growth within and between individual skelet al components, and that gross characterizations of regional rates of g rowth inadequately characterize craniofacial development.