Prevalence of major anatomic variations in oral clefts.

BACKGROUND:The authors describe morphologic variations of oral clefts in a large population-based sample, especially variations in severity and laterality. The authors present 3616 cleft cases treated in Norway for oral clefts between 1967 and 1998. METHODS:Classification of cleft morphology was based on clefting in 9 anatomical focal areas. A three-digit coding system provides a total of 63 possible cleft combinations. Their distribution in the population is presented as a whole and stratified by the baby's sex and the presence of accompanying malformations. The relative proportion of cleft types is illustrated in modified striped Y Kernahan diagrams. RESULTS:Clefts of the lip or palate are more severe when both cleft types are present. Among babies with cleft lip, 18 percent of lips were severe (i.e., complete cleft of the primary palate) in the absence of cleft palate, compared with 81 percent severe when cleft palate was also present. Similarly, among babies with cleft palate, 40 percent were severe (complete cleft of the secondary palate) in the absence of cleft lip, compared with 93 percent when cleft lip was also present. The more severe the cleft lip, the more likely that the baby had an accompanying cleft palate. Girls were more likely to have severe clefts, as were patients who had other types of congenital disabilities. Although cleft lip was more frequent on the left side, clefts were not more severe on the left side. In bilateral cleft lip, the severity was similar on both sides. CONCLUSION:The authors' data provide a population-based reference for common and rare variants of oral clefts.