Genealogical studies in families with oral clefts and reference families

Incidence rates for cleft palate and cleft lip with or without cleft palate appear to be higher in the northeastern part of Västerbotten in northern Sweden (Skellefteá hospital region) than in other hospital regions of the county (Umeå and Lycksele). Data in old parish registers from the Skellefteå region, back to the beginning of the 18th century, are being gradually registered in a local Data Transferral Center connected to the Demographic Database, University of Umeå. From excerpted genealogical data, available at this Center, ancestors to 60 children with oral clefts born in the Skellefteå hospital region (total incidence 2.8 per 1000 liveborn children) and one reference child to each such case, were traced six generations. Pedigrees of ancestors in the four generations elder than the grandparent generation were compared in cleft‐families and reference families by means of a microcomputer. Results suggest that special genes from gene sources in the northern part of the investigated region may have influenced the etiology of different kinds of clefts. Such genes are possibly responsible for the relatively high incidence of oral clefts in the region, which supports an earlier study in which we did not find any connection between oral clefts and emissions from a smelter in the SkellefteÅ region.