[Cleft lip and cleft palate in the Craniofacial Center, Chang Gung Memorial Hospital: incidence, sex, seasonality and topographic distribution].

Of 2963 patients registered at the Chang Gung Craniofacial Center, 1755 patients (906 males and 849 females) who did not have any previous surgery were carefully delineated according to cleft side, involvement of primary or secondary palate and severity of cleft. Cleft lip and palate (43.88%) was the most common cleft, cleft palate (30.88%) the second, while cleft lip (25.24%) the least. More males were found in cleft lip group or cleft lip and palate group, and more females in the cleft palate group. Regarding clefts involving both primary and secondary palates, the cleft of both palates was usually complete, but when the clefts involved either the primary or secondary palate, the cleft was usually incomplete. With regards to the laterality of unilateral cleft lip and/or palate, the left side was affected more than right side. With regard to seasonal variation, cleft palate patients showed the highest incidence from August to October and the lowest incidence from November to January. Cleft lip or cleft lip and palate patients showed the highest incidence from November to February but no obvious difference in the rest of the months. Topographic distribution disclosed that more patients were domiciled in the area north to Hsien-Chu, especially the urban Taipei area.