Premaxillary development in normal and cleft lip and palate human fetuses using three-dimensional computer reconstruction.

As part of an ongoing study of cleft lip and palate fetal morphology, premaxillary development was examined cross-sectionally in a sample of 20 "normal" fetuses and 9 fetuses with complete clefts of the lip and palate ranging in age from 8 to 21 weeks. The specimens were stained with H and E and sectioned at 20 microns in the coronal plane. A computer reconstruction technique was used to produce three-dimensional images of the premaxilla. Premaxillary length and volume were quantified and used to produce fetal growth curves. Qualitatively, normal fetal specimens exhibited symmetrical premaxillary ontogenesis with development of the distinctive perinatal midfacial morphology noted by 14 weeks. In contrast, complete unilateral cleft specimens exhibited severe asymmetry and dysmorphogenesis through 20.5 weeks. Quantitatively, premaxillary length and volume values for the two samples were similar from 8 to 14 weeks and changed in a curvilinear fashion with the steepest increases seen in normal specimens from 14 to 21 weeks. Cleft specimens exhibited significantly (p less than 0.001) reduced premaxillary length and volume rate changes (i.e., slopes of regression lines generated from polynomial and logarithmic regression models) for this time period. Results suggest that premaxillary deficiencies noted clinically in cleft perinates may be related more to early prenatal midfacial growth deficits than initial mesenchymal tissue deficiencies or abnormal growth patterns.