ABSTRACT
BACKGROUND: Most textbooks present data on the various frequencies of clefts in different human "races". This was studied in more detail. MATERIAL AND METHODS: In a major literature study the frequencies of clefting reported in more than 100 publications were studied and the following data was collected: Incidences of clefts in Mongolians, Caucasians and Negroids; relative frequencies of clefts of the primary (and secondary) palate versus that of clefts of the secondary palate (only); data on cleft location (right, left, bilateral) and on genders affected. RESULTS: There was most confusing data on incidences in the different "races" whilst all other data was rather consistent: complete clefts (i.e. primary plus secondary palate affected) were most common with left sided ones being reported most often; males were more prone to have a cleft of the primary palate than females and females were more often affected by clefts of the secondary palate than males. DISCUSSION: The types of data bases having been evaluated varied from report to report indicating that today's data pools are of different qualities. Regional or national registries are necessary to collect reliable data with strict definitions applied in all countries.
