Prenatal growth of the median face.

The growth and development of the median facial region remain incompletely understood. Data concerning the prenatal size and growth rates of facial components are especially lacking. A group of fetuses and newborn infants with apparently normal craniofacial development and body size was therefore studied at autopsy. The interorbital distance and dimensions of the external nose, philtrum (upper lip), and mouth were determined; the growth of morphogenetically related structures--the ethmoid bone and tongue--was also studied. The slopes of linear regressions of these variables against body length indicated that growth of the median facial region proceeds slowly in the latter half of gestation. The center of the face seems to grow slower than the sides of the face. A multivariate technique, factor analysis, identified and ordered relationships among the variables. The best statistical summary of size in the median face was given by four transversely oriented variables, nose breadth, outer orbital distance, inner canthal distance, and mouth width. Within the region, a secondary cluster was dominated by sagittally oriented variables. The second best summary of median facial relationships was provided by three variables of lingual size and was followed by a group of variables representing ethmoidal size. This pattern of growth may represent the effects of a developmental hierarchy. Growth seems to be coordinated along the major axes of the body, with transverse growth controlled more rigidly than sagittal growth. The statistical independence of the three regions suggests that the controls of growth are also separate.