EFFECTS OF FETUS WEIGHT, DAM STRAIN, DAM WEIGHT, AND LITTER SIZE ON THE CRANIOFACIAL MORPHOGENESIS OF CL FR MOUSE FETUSES AFFECTED WITH CLEFT-LIP AND PALATE/

Objective: This study examined the factors related to the morphogenesi s of the craniofacial complex of the CL/Fr mouse fetus affected with C LP based on the findings of a lateral cephalogram. Design: Embryo tran sfer experiments were performed to determine the effect of the fetus w eight, dam strain, dam weight, and litter size on the intra-uterine cr aniofacial morphogenesis of CL/Fr mouse fetuses. On the 18th gestation al day, each pregnant dam that had received CL/Fr mouse embryos was la parotomized to remove the transferred fetuses that had developed in th e uteri of the cleft lip and palate (CLP)-susceptible CL/Fr strain dam and the CLP-resistant C57BL strain dam. A cephalometric observation o f the craniofacial morphology of each fetus was subsequently performed . Results: Based on a multiple regression analysis, the standardized p artial regression coefficients of the affected fetus weight, the dam w eight, and the litter size on the maxillary size of the affected CL/Fr fetus were 0.71 (p < .01), 0.03, and -0.07. According to a least-squa res analysis of variance, the dam strain effect in addition to the eff ect of the affected fetus weight on the maxillary size and the cranial size of the affected fetuses was significant (p < .01 for cranial siz e, p < .05 for maxillary size) and close to a significant lever (p = . 09) for the mandibular size of the affected fetuses. The adjusted maxi llary size and cranial size after statistically eliminating the effect s of the affected fetus weight, dam weight, and litter size on each or iginal craniofacial size of the affected fetuses that had developed in the CL/Fr dam strain were also significantly smaller than those of th e affected fetuses that had developed in the C57BL dam strain. Conclus ions: The present results indicate that the craniofacial growth of the CL/Fr mouse fetus affected with CLP increased in proportion to the fe tus weight. The dam strain effect, in addition to the effect of the af fected fetus weight, could thus not be ignored when the etiology of th e spontaneous CLP was examined, while the uterine environment, provide d by the CL/Fr strain dam, retarded the intra-uterine craniofacial gro wth of the affected fetuses. It was therefore concluded that the dam s train effect, as well as the effect of the affected fetus weight, both play an important role on the craniofacial morphogenesis of the CL/Fr strain of the affected fetuses that developed in both strain dams.