Incidence rates for cleft lip and palate in British Columbia 1952-71 for North American Indian, Japanese, Chinese and total populations: secular trends over twenty years.

The incidence of cleft lip and/or cleft palate was examined for the 1952-71 period for the Province of British Columbia. Although there were some fluctuations, some of which were significant, there was no general trend which indicated that the rates were either increasing or decreasing. These rates are important for a background calculation when investigating new invironment teratogens. The total rate of 1.97 per 1,000 live birth is comparable with other Caucasian populations where there is good ascertainment and adequate follow-up period. This study also confirmed the previously reported high rate for North American Indians in British Columbia (3.74 per 1,000 live births) and established rates for the Japanese (3.36 per 1,000 live births) and Chinese (1.76 per 1,000 live births) of British Columbia. Since these three sub-populations are relatively small in relation to the total population, they do not influence the overall total rate to any great extent.