The distribution of clefts of the primary and secondary palates by sex, type, and location.

The frequency and patterns of distribution of cleft lip, cleft lip and alveolus, cleft lip and palate, and isolated cleft palate, together with the possible association between sex, type of cleft, and affected side were studied from records of 278 individuals with clefts. These records were obtained from four cleft centers in the New York City area and constituted a racially mixed urban sample. The type of the cleft varied between sexes. Males had significantly higher rates of cleft lip and palate (p<0.0001), and females had higher rates of isolated cleft palate (p<0.0001). No sex differences were found for cleft lip or cleft lip and alveolus. Unilateral clefts of both the primary and secondary palates were found to occur over three times more frequently than bilateral clefts, and left side predominance was demonstrated.