Incidence and aetiology of oral clefts: a review.

Craniofacial anomalies, most especially cleft lip and palate, are major human birth deformities with a world wide incidence of 1 in 700 and associated substantial clinical and psychosocial impact. Wide ranges of studies in developmental biology have shown that both genetics and environmental factors are involved in the etiology of oral clefts. However, genetics of cleft lip alone or accompanied by cleft palate, are different from those of isolated cleft palate. The prevention of oral clefts is not possible without knowing the precise etiology. Genetic counseling can now identify high risk families; the clefts themselves may be visible at 20 weeks gestation, but beyond early identification, we can only look into the future on the possibility of preventing oral clefts. This article reviews the available literature on the gene-environment contributions to nonsyndromic forms of clefting and their implication for possible preventive measures.