Ethnic differences in the incidence of cleft lip and/or cleft palate in Auckland, 1960-1976.

The incidence of facial clefts among live births in the Auckland urban area has been studied for the years 1960-1976. After correction for ascertainment, the live-born incidence of non-syndromal cleft palate among Maoris was 1.867/1000, and among Europeans it was 0.643/1000. The incidences for non-syndromal cleft lip, with or without cleft palate, were 0.397/1000 for Maoris, and 1.195/1000 for Europeans. The sex ratio for cleft palate showed the usual female preponderance, although there was evidence of heterogeneity between the races. Cleft lip occurred more commonly among males. Birth rank, maternal age, and paternal age had no apparent effect on the incidences, and there were no significant secular or seasonal changes in incidence.