Facial clefting and Amerindian admixture in populations of Santiago, Chile.

Among congenital malformations, cleft lip with and/or without cleft palate has the highest relative frequencies and shows ethnic variation in prevalence. Both malformations are generally more common among the Asian than European populations. Many populations of Chile have genes of Amerindian and Spanish ancestry, with considerable variation in the degree of Amerindian admixture. Therefore, the association of clefting incidence with Amerindian admixture was investigated. The frequency of cleft lip and/or cleft palate in infants born in three private and two public maternity service clinics of Santiago, Chile, is reported. The private clinic patients have a higher socioeconomic status (SES) than those receiving the public services. They also differ in estimated Amerindian admixture. More than 200,900 consecutive birth records were reviewed. The rate of clefting malformations is 15.3 per 10,000 live births. Based on allele frequencies at the ABO and Rh blood group loci, the percentage of Amerindian admixture is higher in infants born in the public compared to those born in the private maternity service clinics. Amerindian admixture is positively correlated (Spearman's p = 0.9, P = 0.008) with clefting rate across these samples. Clefting is also associated with SES, with lower SES showing higher clefting rates. Mothers of clefting newborns also have higher estimated Amerindian admixture compared to those of normal newborns. The results support the view that in Chilean populations, susceptibility to clefting is related to Amerindian ancestry. Am. J. Hum. Biol. 9:225-232, 1997. © 1997 Wiley-Liss, Inc.