An epidemiological and genetic study of facial clefting in France. I. Epidemiology and frequency in relatives

The frequencies of cleft lip with or without cleft palate (CL(P)) and isolated cleft palate (CP) have been estimated in France to be 0.082% and 0.035%, respectively, after exclusion of malformation syndromes. A genetic and epidemiological study has been carried out on 468 patients with CL(P) and 163 with CP. The results are given in detail and some specific points are discussed: the apparently low incidence in France, the relationship between sex ratio and abortion rates, the maternal effects, and the possibility of an association between CL(P) and CP.